Immunoglobulin domain; The members here are composed of the immunoglobulin (Ig) domain found in the Ig superfamily. The Ig superfamily is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. Members of this group are components of immunoglobulin, neuroglia, cell surface glycoproteins, including T-cell receptors, CD2, CD4, CD8, and membrane glycoproteins, including butyrophilin and chondroitin sulfate proteoglycan core protein. A predominant feature of most Ig domains is a disulfide bridge connecting the two beta-sheets with a tryptophan residue packed against the disulfide bond. Ig superfamily (IgSF) domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Typically, the V-set domains have A, B, E, and D strands in one sheet and A', G, F, C, C' and C" in the other. The structures in C1-set are smaller than those in the V-set; they have one beta sheet that is formed by strands A, B, E, and D and the other by strands G, F, C, and C'. Moreover, a C1-set Ig domain contains a short C' strand (three residues) and lacks A' and C" strand. Unlike other Ig domain sets, C2-set structures do not have a D strand. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804 183 PYISKAKNTGVSVGQKGILSCEASAV-PMAEFQWFKEETRLATGLD-GMRIENKGRMSTLTFFNVSEKDYGNYTCVATNK 260
Cdd:cd05750    1 PKLKEMKSQTVQEGSKLVLKCEATSEnPSPRYRWFKDGKELNRKRPkNIKIRNKKKNSELQINKAKLEDSGEYTCVVENI 80

                         90
                 ....*....|.
gi 981220804 261 LGNTNASITLY 271
Cdd:cd05750   81 LGKDTVTGNVT 91

Immunoglobulin domain; The members here are composed of the immunoglobulin (Ig) domain found in the Ig superfamily. The Ig superfamily is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. Members of this group are components of immunoglobulin, neuroglia, cell surface glycoproteins, including T-cell receptors, CD2, CD4, CD8, and membrane glycoproteins, including butyrophilin and chondroitin sulfate proteoglycan core protein. A predominant feature of most Ig domains is a disulfide bridge connecting the two beta-sheets with a tryptophan residue packed against the disulfide bond. Ig superfamily (IgSF) domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Typically, the V-set domains have A, B, E, and D strands in one sheet and A', G, F, C, C' and C" in the other. The structures in C1-set are smaller than those in the V-set; they have one beta sheet that is formed by strands A, B, E, and D and the other by strands G, F, C, and C'. Moreover, a C1-set Ig domain contains a short C' strand (three residues) and lacks A' and C" strand. Unlike other Ig domain sets, C2-set structures do not have a D strand. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804   3 NVTVRQGESATLRCTIDDRV-TRVAWLN--RSTILYagNDKWSI-DPRVIILVNTPTQYSIMIQNVDVYDEGPYTCSVQT 78
Cdd:cd05717    5 DVTVVEGETLTLKCQVSLRDdSSLQWLNpnGQTIYF--NDKRALrDSRYQLLNHSASELSISVSNVTLSDEGVYTCLHYT 82

                         90
                 ....*....|...
gi 981220804  79 DNhPKTSRVHLIV 91
Cdd:cd05717   83 DP-VSTKKVTVTV 94

Immunoglobulin (Ig)-like domain in neuregulins; The members here are composed of the immunoglobulin (Ig)-like domain in neuregulins (NRGs). NRGs are signaling molecules which participate in cell-cell interactions in the nervous system, breast, heart, and other organ systems, and are implicated in the pathology of diseases including schizophrenia, multiple sclerosis, and breast cancer. There are four members of the neuregulin gene family (NRG-1, NRG-2, NRG-3, and NRG-4). The NRG-1 protein, binds to and activates the tyrosine kinases receptors ErbB3 and ErbB4, initiating signaling cascades. The other NRGs proteins bind one or the other or both of these ErbBs. NRG-1 has multiple functions: in the brain it regulates various processes such as radial glia formation and neuronal migration, dendritic development, and expression of neurotransmitters receptors, while in the peripheral nervous system NRG-1 regulates processes such as target cell differentiation, and Schwann cell survival. There are many NRG-1 isoforms which arise from the alternative splicing of mRNA. Less is known of the functions of the other NRGs. NRG-2 and NRG-3 are expressed predominantly in the nervous system. NRG-2 is expressed by motor neurons and terminal Schwann cells, and is concentrated near synaptic sites and may be a signal that regulates synaptic differentiation. NRG-4 has been shown to direct pancreatic islet cell development towards the delta-cell lineage.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804 183 PYISKAKNTGVSVGQKGILSCEASAV-PMAEFQWFKEETRLATGLD-GMRIENKGRMSTLTFFNVSEKDYGNYTCVATNK 260
Cdd:cd05750    1 PKLKEMKSQTVQEGSKLVLKCEATSEnPSPRYRWFKDGKELNRKRPkNIKIRNKKKNSELQINKAKLEDSGEYTCVVENI 80

                         90
                 ....*....|.
gi 981220804 261 LGNTNASITLY 271
Cdd:cd05750   81 LGKDTVTGNVT 91

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 981220804  182 PPYIS-KAKNTGVSVGQKGILSCEASAVPMAEFQWFKEETRLATGLDGMRIENKGRmSTLTFFNVSEKDYGNYTCVATN 259
Cdd:pfam13927   1 KPVITvSPSSVTVREGETVTLTCEATGSPPPTITWYKNGEPISSGSTRSRSLSGSN-STLTISNVTRSDAGTYTCVASN 78

First (N-terminal) immunoglobulin (Ig)-like domain of the nectin-like molecules; member of the V-set of Ig superfamily (IgSF) domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of the nectin-like molecules Necl-1 (also known as cell adhesion molecule 3 (CADM3)), Necl-2 (CADM1), Necl-3 (CADM2), and similar proteins. At least five nectin-like molecules have been identified (Necl-1 to Necl-5). They all have an extracellular region containing three Ig-like domains, a transmembrane region, and a cytoplasmic region. The N-terminal Ig-like domain of the extracellular region belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-1, Necl-2, and Necl-3 have Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-1 is specifically expressed in neural tissue, and is important to the formation of synapses, axon bundles, and myelinated axons. Necl-2 is expressed in a wide variety of tissues and is a putative tumour suppressor gene which is downregulated in aggressive neuroblastoma. Necl-3 accumulates in central and peripheral nervous system tissue and has been shown to selectively interact with oligodendrocytes. This group also contains Class-I MHC-restricted T-cell-associated molecule (CRTAM), whose expression pattern is consistent with its expression in Class-I MHC-restricted T-cells.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804   3 NVTVRQGESATLRCTIDDRV-TRVAWLN--RSTILYagNDKWSI-DPRVIILVNTPTQYSIMIQNVDVYDEGPYTCSVQT 78
Cdd:cd05717    5 DVTVVEGETLTLKCQVSLRDdSSLQWLNpnGQTIYF--NDKRALrDSRYQLLNHSASELSISVSNVTLSDEGVYTCLHYT 82

                         90
                 ....*....|...
gi 981220804  79 DNhPKTSRVHLIV 91
Cdd:cd05717   83 DP-VSTKKVTVTV 94

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804     3 NVTVRQGESATLRCTI-DDRVTRVAWLNrstilyaGNDKWSIDPRVIILVNTPTQYSIMIQNVDVYDEGPYTCSVQTDNH 81
Cdd:smart00410   3 SVTVKEGESVTLSCEAsGSPPPEVTWYK-------QGGKLLAESGRFSVSRSGSTSTLTISNVTPEDSGTYTCAATNSSG 75

                           90
                   ....*....|
gi 981220804    82 PKTSRVHLIV 91
Cdd:smart00410  76 SASSGTTLTV 85

Immunoglobulin V-set domain; This domain is found in antibodies as well as neural protein P0 and CTL4 amongst others.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804    4 VTVRQGESATLRCTI----DDRVTRVAWL-------NRSTILYAGND--KWSIDPRVIILVNTP-TQYSIMIQNVDVYDE 69
Cdd:pfam07686   6 VTVALGGSVTLPCTYsssmSEASTSVYWYrqppgkgPTFLIAYYSNGseEGVKKGRFSGRGDPSnGDGSLTIQNLTLSDS 85

                          90       100
                  ....*....|....*....|...
gi 981220804   70 GPYTCSVQTDNHPKTSR-VHLIV 91
Cdd:pfam07686  86 GTYTCAVIPSGEGVFGKgTRLTV 108

Immunoglobulin (Ig)-like domain in neuregulins; The members here are composed of the immunoglobulin (Ig)-like domain in neuregulins (NRGs). NRGs are signaling molecules which participate in cell-cell interactions in the nervous system, breast, heart, and other organ systems, and are implicated in the pathology of diseases including schizophrenia, multiple sclerosis, and breast cancer. There are four members of the neuregulin gene family (NRG-1, NRG-2, NRG-3, and NRG-4). The NRG-1 protein, binds to and activates the tyrosine kinases receptors ErbB3 and ErbB4, initiating signaling cascades. The other NRGs proteins bind one or the other or both of these ErbBs. NRG-1 has multiple functions: in the brain it regulates various processes such as radial glia formation and neuronal migration, dendritic development, and expression of neurotransmitters receptors, while in the peripheral nervous system NRG-1 regulates processes such as target cell differentiation, and Schwann cell survival. There are many NRG-1 isoforms which arise from the alternative splicing of mRNA. Less is known of the functions of the other NRGs. NRG-2 and NRG-3 are expressed predominantly in the nervous system. NRG-2 is expressed by motor neurons and terminal Schwann cells, and is concentrated near synaptic sites and may be a signal that regulates synaptic differentiation. NRG-4 has been shown to direct pancreatic islet cell development towards the delta-cell lineage.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804 183 PYISKAKNTGVSVGQKGILSCEASAV-PMAEFQWFKEETRLATGLD-GMRIENKGRMSTLTFFNVSEKDYGNYTCVATNK 260
Cdd:cd05750    1 PKLKEMKSQTVQEGSKLVLKCEATSEnPSPRYRWFKDGKELNRKRPkNIKIRNKKKNSELQINKAKLEDSGEYTCVVENI 80

                         90
                 ....*....|.
gi 981220804 261 LGNTNASITLY 271
Cdd:cd05750   81 LGKDTVTGNVT 91

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 981220804  182 PPYIS-KAKNTGVSVGQKGILSCEASAVPMAEFQWFKEETRLATGLDGMRIENKGRmSTLTFFNVSEKDYGNYTCVATN 259
Cdd:pfam13927   1 KPVITvSPSSVTVREGETVTLTCEATGSPPPTITWYKNGEPISSGSTRSRSLSGSN-STLTISNVTRSDAGTYTCVASN 78

Immunoglobulin domain; Members of the immunoglobulin superfamily are found in hundreds of proteins of different functions. Examples include antibodies, the giant muscle kinase titin and receptor tyrosine kinases. Immunoglobulin-like domains may be involved in protein-protein and protein-ligand interactions.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804  186 SKAKNTGVSVGQKGILSCEAS-AVPMAEFQWFKEETRLATGLDGMRIENKGRMSTLTFFNVSEKDYGNYTCVATNKLGNT 264
Cdd:pfam00047   1 SAPPTVTVLEGDSATLTCSAStGSPGPDVTWSKEGGTLIESLKVKHDNGRTTQSSLLISNVTKEDAGTYTCVVNNPGGSA 80

                  ....*.
gi 981220804  265 NASITL 270
Cdd:pfam00047  81 TLSTSL 86

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 981220804   95 PQIMNISSDITVNEGSSVTLLCLAIGRPEPTVTWRH--LSVKEGQGFV---SEDEY-LEISDIKRDQSGEYECSALNDV 167
Cdd:pfam07679   1 PKFTQKPKDVEVQEGESARFTCTVTGTPDPEVSWFKdgQPLRSSDRFKvtyEGGTYtLTISNVQPDDSGKYTCVATNSA 79

Fourth immunoglobulin domain of the Drosophila melanogaster Dscam protein, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin domain of the Drosophila melanogaster Down syndrome cell adhesion molecule (DSCAM) protein and similar proteins. Down syndrome cell adhesion molecule (DSCAM) is a cell adhesion molecule that plays critical roles in neural development, including axon guidance and branching, axon target recognition, self-avoidance and synaptic formation. DSCAM belongs to the immunoglobulin superfamily and contributes to defects in the central nervous system in Down syndrome patients. Vertebrate DSCAMs differ from Drosophila Dscam1 in that they lack the extensive alternative splicing that occurs in the insect gene. Drosophila melanogaster Dscam has 38,016 isoforms generated by the alternative splicing of four variable exon clusters, which allows every neuron in the fly to display a distinctive set of Dscam proteins on its cell surface. Drosophila Dscam1 is a cell-surface protein that plays important roles in neural development and axon tiling of neurons. It is shown that thousands of isoforms bind themselves through specific homophilic (self-binding) interactions, a process which mediates cellular self-recognition. Drosophila Dscam2 is also alternatively spliced and plays a key role in the development of two visual system neurons, monopolar cells L1 and L2. This group is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804  94 PPQIMNISSDITVNEGSSVTLLCLAIGRPEPTVTWR--HLSVKEGQGF-----VSED----EYLEISDIKRDQSGEYECS 162
Cdd:cd20956    1 APVLLETFSEQTLQPGPSVSLKCVASGNPLPQITWTldGFPIPESPRFrvgdyVTSDgdvvSYVNISSVRVEDGGEYTCT 80

                 ....*..
gi 981220804 163 ALNDVAA 169
Cdd:cd20956   81 ATNDVGS 87

agrin-responsive first immunoglobulin-like domains (Ig1) of the MuSK ectodomain; a member of the I-set of IgSF domains; The members here are composed of the first immunoglobulin-like domains (Ig1) of the Muscle-specific kinase (MuSK). MuSK is a receptor tyrosine kinase specifically expressed in skeletal muscle, where it plays a central role in the formation and maintenance of the neuromuscular junction (NMJ). MuSK is activated by agrin, a neuron-derived heparan sulfate proteoglycan. The activation of MUSK in myotubes regulates the formation of NMJs through the regulation of different processes including the specific expression of genes in subsynaptic nuclei, the reorganization of the actin cytoskeleton and the clustering of the acetylcholine receptors (AChR) in the postsynaptic membrane. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of the MuSK lacks this strand and thus it belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804  90 IVQVPPQimniSSDITVNEGSSVTLLCLAIGRPEPTVTWRHLSVK-----EGQGFVSEDEYLEISDIKRDQSGEYECSAL 164
Cdd:cd20970    2 VISTPQP----SFTVTAREGENATFMCRAEGSPEPEISWTRNGNLiiefnTRYIVRENGTTLTIRNIRRSDMGIYLCIAS 77

                         90
                 ....*....|....*
gi 981220804 165 NDVAAPDVRKVKITV 179
Cdd:cd20970   78 NGVPGSVEKRITLQV 92

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804     3 NVTVRQGESATLRCTI-DDRVTRVAWLNrstilyaGNDKWSIDPRVIILVNTPTQYSIMIQNVDVYDEGPYTCSVQTDNH 81
Cdd:smart00410   3 SVTVKEGESVTLSCEAsGSPPPEVTWYK-------QGGKLLAESGRFSVSRSGSTSTLTISNVTPEDSGTYTCAATNSSG 75

                           90
                   ....*....|
gi 981220804    82 PKTSRVHLIV 91
Cdd:smart00410  76 SASSGTTLTV 85

Second Ig-like domain of the giant muscle protein titin Z1z2 in the sarcomeric Z-disk, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig)-like domain of the giant muscle protein titin Z1z2 in the sarcomeric Z-disk and similar proteins. Titin is a key component in the assembly and functioning of vertebrate striated muscles. By providing connections at the level of individual microfilaments, it contributes to the fine balance of forces between the two halves of the sarcomere. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of the titin Z1z2 lacks this strand and thus it belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804 182 PPYISKAKNTGVSVGQKGILSCEASAVPMAEFQWFKEETRLATGLDgMRIENKGRMSTLTFFNVSEKDYGNYTCVATNKL 261
Cdd:cd20972    2 PQFIQKLRSQEVAEGSKVRLECRVTGNPTPVVRWFCEGKELQNSPD-IQIHQEGDLHSLIIAEAFEEDTGRYSCLATNSV 80

                         90
                 ....*....|
gi 981220804 262 GNTNASITLY 271
Cdd:cd20972   81 GSDTTSAEIF 90

First (N-terminal) immunoglobulin (Ig)-like domain of nectin-like molecule-1 (Necl-1); member of the V-set of Ig superfamily (IgSF) domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of nectin-like molecule-1, Necl-1 (also known as celll adhesion molecule 3 (CADM3), SynCAM2, or IGSF4). Nectin-like molecules have similar domain structures to those of nectins. At least five nectin-like molecules have been identified (Necl-1 - Necl-5). They all have an extracellular region containing three Ig-like domains, a transmembrane region, and a cytoplasmic region. The N-terminal Ig-like domain of the extracellular region belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-1 has Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-1 is specifically expressed in neural tissue and is important to the formation of synapses, axon bundles, and myelinated axons.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 981220804   3 NVTVRQGESATLRCTIDDRV-TRVAWLNRST-ILYAGNDKWSIDPRVIILVNTPTQYSIMIQNVDVYDEGPYTCSVQT 78
Cdd:cd05882    6 DETVAVGGTVTLKCGVKEHDnSSLQWSNTAQqTLYFGEKRALRDNRIQLVKSTPTELIISISNVQLSDEGEYTCSIFT 83

C-terminal immunoglobulin-like domain of the myosin-associated giant protein kinase Twitchin, and similar domains; member of the I-set IgSF domains; The members here are composed of the C-terminal immunoglobulin-like domain of the myosin-associated giant protein kinase Twitchin and similar proteins, including Caenorhabditis elegans and Aplysia californica Twitchin, Drosophila melanogaster Projectin, and similar proteins. These are very large muscle proteins containing multiple immunoglobulin (Ig)-like and fibronectin type III (FN3) domains and a single kinase domain near the C-terminus. In humans these proteins are called Titin. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. The Ig-like domain of the Twitchin is a member of the I-set IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins (titin, telokin, and twitchin), the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 981220804 104 ITVNEGSSVTLLCLAIGRPEPTVTW----RHLS--VKEGQGFVSEDEYLEISDIKRDQSGEYECSALN 165
Cdd:cd20949    9 TTVKEGQSATILCEVKGEPQPNVTWhfngQPISasVADMSKYRILADGLLINKVTQDDTGEYTCRAYQ 76

Third immunoglobulin (Ig)-like domain of Neural Cell Adhesion Molecule 1 (NCAM-1); member of the I-set of IgSF domains; The members here are composed of the third immunoglobulin (Ig)-like domain of Neural Cell Adhesion Molecule (NCAM-1). NCAM plays important roles in the development and regeneration of the central nervous system, in synaptogenesis and neural migration. NCAM mediates cell-cell and cell-substratum recognition and adhesion via homophilic (NCAM-NCAM), and heterophilic (NCAM-non-NCAM), interactions. NCAM is expressed as three major isoforms having different intracellular extensions. The extracellular portion of NCAM has five N-terminal Ig-like domains and two fibronectin type III domains. The double zipper adhesion complex model for NCAM homophilic binding involves Ig1, Ig2, and Ig3. By this model, Ig1 and Ig2 mediate dimerization of NCAM molecules situated on the same cell surface (cis interactions), and Ig3 domains mediate interactions between NCAM molecules expressed on the surface of opposing cells (trans interactions) through binding to the Ig1 and Ig2 domains. The adhesive ability of NCAM is modulated by the addition of polysialic acid chains to the fifth Ig-like domain.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804 170 PDVRKVKITVNyppyisKAKNTGVSVgqkgILSCEASAVPMAEFQWFKEETRLATGLDGMRIENKGrmSTLTFFNVSEKD 249
Cdd:cd05730    2 PTIRARQSEVN------ATANLGQSV----TLACDADGFPEPTMTWTKDGEPIESGEEKYSFNEDG--SEMTILDVDKLD 69

                         90       100
                 ....*....|....*....|.
gi 981220804 250 YGNYTCVATNKLGNTNASITL 270
Cdd:cd05730   70 EAEYTCIAENKAGEQEAEIHL 90

Third immunoglobulin (Ig)-like domain of Neural Cell Adhesion Molecule 1 (NCAM-1); member of the I-set of IgSF domains; The members here are composed of the third immunoglobulin (Ig)-like domain of Neural Cell Adhesion Molecule (NCAM-1). NCAM plays important roles in the development and regeneration of the central nervous system, in synaptogenesis and neural migration. NCAM mediates cell-cell and cell-substratum recognition and adhesion via homophilic (NCAM-NCAM), and heterophilic (NCAM-non-NCAM), interactions. NCAM is expressed as three major isoforms having different intracellular extensions. The extracellular portion of NCAM has five N-terminal Ig-like domains and two fibronectin type III domains. The double zipper adhesion complex model for NCAM homophilic binding involves Ig1, Ig2, and Ig3. By this model, Ig1 and Ig2 mediate dimerization of NCAM molecules situated on the same cell surface (cis interactions), and Ig3 domains mediate interactions between NCAM molecules expressed on the surface of opposing cells (trans interactions) through binding to the Ig1 and Ig2 domains. The adhesive ability of NCAM is modulated by the addition of polysialic acid chains to the fifth Ig-like domain.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804  94 PP--QIMNISSDITVNEGSSVTLLCLAIGRPEPTVTWRhlsvKEGQGFVSEDEY---------LEISDIKRDQSGEYECS 162
Cdd:cd05730    1 PPtiRARQSEVNATANLGQSVTLACDADGFPEPTMTWT----KDGEPIESGEEKysfnedgseMTILDVDKLDEAEYTCI 76

                 ...
gi 981220804 163 ALN 165
Cdd:cd05730   77 AEN 79

Immunoglobulin domain; This domain contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 981220804  193 VSVGQKGILSCEASAVPMAEFQWFKeetrlatglDGMRIENKGRMSTLtffNVSEKDYGNYTCVATN-KLGNTNASITL 270
Cdd:pfam13895  11 VTEGEPVTLTCSAPGNPPPSYTWYK---------DGSAISSSPNFFTL---SVSAEDSGTYTCVARNgRGGKVSNPVEL 77

Fourth immunoglobulin (Ig)-like domain of hemolin, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain of hemolin and similar proteins. Hemolin, an insect immunoglobulin superfamily (IgSF) member containing four Ig-like domains, is a lipopolysaccharide-binding immune protein induced during bacterial infection. Hemolin shares significant sequence similarity with the first four Ig-like domains of the transmembrane cell adhesion molecules (CAMs) of the L1 family. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. The fourth Ig-like domain of hemolin is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set domains, members of the I-set have a discontinuous A strand but lack a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 981220804  94 PPQIMNISSDITVNEGSSVTLLCLAIGRPEPTVTW----RHLSVKEGQGFVsEDEYLEISDIKRDQSGEYECSALN 165
Cdd:cd20978    1 PKFIQKPEKNVVVKGGQDVTLPCQVTGVPQPKITWlhngKPLQGPMERATV-EDGTLTIINVQPEDTGYYGCVATN 75

Fourth immunoglobulin (Ig)-like domain of hemolin, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain of hemolin and similar proteins. Hemolin, an insect immunoglobulin superfamily (IgSF) member containing four Ig-like domains, is a lipopolysaccharide-binding immune protein induced during bacterial infection. Hemolin shares significant sequence similarity with the first four Ig-like domains of the transmembrane cell adhesion molecules (CAMs) of the L1 family. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. The fourth Ig-like domain of hemolin is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set domains, members of the I-set have a discontinuous A strand but lack a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804 182 PPYISKA-KNTGVSVGQKGILSCEASAVPMAEFQWFKEETRLaTGLDGMRIENKGrmsTLTFFNVSEKDYGNYTCVATNK 260
Cdd:cd20978    1 PKFIQKPeKNVVVKGGQDVTLPCQVTGVPQPKITWLHNGKPL-QGPMERATVEDG---TLTIINVQPEDTGYYGCVATNE 76

                         90
                 ....*....|.
gi 981220804 261 LGNTNASITLY 271
Cdd:cd20978   77 IGDIYTETLLH 87

Third immunoglobulin (Ig)-like domain in Robo (roundabout) receptors; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the third immunoglobulin (Ig)-like domain in Robo (roundabout) receptors. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, Robo2, Robo3), and three mammalian Slit homologs (Slit-1,Slit-2, Slit-3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, Robo2, and Robo3 are expressed by commissural neurons in the vertebrate spinal cord and Slit-1, Slit-2, and Slit-3 are expressed at the ventral midline. Robo-3 is a divergent member of the Robo family which instead of being a positive regulator of Slit responsiveness, antagonizes Slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit2 has been shown by surface plasmon resonance experiments and mutational analysis to be the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804 185 ISKAKNTGVSVGQKGILSCEASAVPMAEFQWFKEETRLATGLDGMRIENkgrmsTLTFFNVSEKDYGNYTCVATNKLGNT 264
Cdd:cd05725    1 VKRPQNQVVLVDDSAEFQCEVGGDPVPTVRWRKEDGELPKGRYEILDDH-----SLKIRKVTAGDMGSYTCVAENMVGKI 75

                 ....*.
gi 981220804 265 NASITL 270
Cdd:cd05725   76 EASATL 81

Immunoglobulin (Ig)-like I-set domain of Neural Cell Adhesion Molecule 2 (NCAM-2); The members here are composed of the fourth Ig domain of Neural Cell Adhesion Molecule NCAM-2 (also known as OCAM/mamFas II and RNCAM). NCAM-2 is organized similarly to NCAM, including five N-terminal Ig-like domains and two fibronectin type III domains. NCAM-2 is differentially expressed in the developing and mature olfactory epithelium (OE), and may function like NCAM, as an adhesion molecule. One of the unique features of I-set domains is the lack of a C" strand. The structures of this group show that the Ig domain lacks this strand and thus is a member of the I-set of Ig domains.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804  93 VPPQIMNISSDITVnEGSSVTLLCLAIGRPEPTVTWRHLSvkEGQGFVSEDE---------------YLEISDIKRDQSG 157
Cdd:cd05870    1 VQPHIIQLKNETTV-ENGAATLSCKAEGEPIPEITWKRAS--DGHTFSEGDKspdgrievkgqhgesSLHIKDVKLSDSG 77

                         90
                 ....*....|
gi 981220804 158 EYECSALNDV 167
Cdd:cd05870   78 RYDCEAASRI 87

agrin-responsive first immunoglobulin-like domains (Ig1) of the MuSK ectodomain; a member of the I-set of IgSF domains; The members here are composed of the first immunoglobulin-like domains (Ig1) of the Muscle-specific kinase (MuSK). MuSK is a receptor tyrosine kinase specifically expressed in skeletal muscle, where it plays a central role in the formation and maintenance of the neuromuscular junction (NMJ). MuSK is activated by agrin, a neuron-derived heparan sulfate proteoglycan. The activation of MUSK in myotubes regulates the formation of NMJs through the regulation of different processes including the specific expression of genes in subsynaptic nuclei, the reorganization of the actin cytoskeleton and the clustering of the acetylcholine receptors (AChR) in the postsynaptic membrane. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of the MuSK lacks this strand and thus it belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 981220804 186 SKAKNTGVSVGQKGILSCEASAVPMAEFQWFKEETRLATGLDGMRIENKGRMstLTFFNVSEKDYGNYTCVATNKLGNT 264
Cdd:cd20970    7 QPSFTVTAREGENATFMCRAEGSPEPEISWTRNGNLIIEFNTRYIVRENGTT--LTIRNIRRSDMGIYLCIASNGVPGS 83

Immunoglobulin (Ig)-like I-set domain of Neural Cell Adhesion Molecule 1 (NCAM-1) and similar proteins; The members here are composed of the fourth immunoglobulin (Ig)-like domain of Neural Cell Adhesion Molecule (NCAM-1). NCAM plays important roles in the development and regeneration of the central nervous system, in synaptogenesis and neural migration. NCAM mediates cell-cell and cell-substratum recognition and adhesion via homophilic (NCAM-NCAM), and heterophilic (NCAM-non-NCAM), interactions. NCAM is expressed as three major isoforms having different intracellular extensions. The extracellular portion of NCAM has five N-terminal Ig-like domains and two fibronectin type III domains. The double zipper adhesion complex model for NCAM homophilic binding involves Ig1, Ig2, and Ig3. By this model, Ig1 and Ig2 mediate dimerization of NCAM molecules situated on the same cell surface (cis interactions), and Ig3 domains mediate interactions between NCAM molecules expressed on the surface of opposing cells (trans interactions), through binding to the Ig1 and Ig2 domains. The adhesive ability of NCAM is modulated by the addition of polysialic acid chains to the fifth Ig-like domain. Also included in this group is NCAM-2 (also known as OCAM/mamFas II and RNCAM) NCAM-2 is differentially expressed in the developing and mature olfactory epithelium (OE). One of the unique features of I-set domains is the lack of a C" strand. The structures of this group show that the Ig domain lacks this strand and thus is a member of the I-set of Ig domains.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804  93 VPPQIMNISSDITVnEGSSVTLLCLAIGRPEPTVTWR---------------HLSVKEGQGFVSedeyLEISDIKRDQSG 157
Cdd:cd05732    1 VQPKITYLENQTAV-ELEQITLTCEAEGDPIPEITWRratrgisfeegdldgRIVVRGHARVSS----LTLKDVQLTDAG 75

                 ....*...
gi 981220804 158 EYECSALN 165
Cdd:cd05732   76 RYDCEASN 83

First immunoglobulin (Ig)-like constant domain in Robo (roundabout) receptors, and similar domains; The members here are composed of the first immunoglobulin (Ig)-like domain in Roundabout (Robo) receptors. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, Robo2, and Robo3), and three mammalian Slit homologs (Slit1, Slit2, Slit3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, Robo2, and Robo3 are expressed by commissural neurons in the vertebrate spinal cord and Slit1, Slit2,and Slit3 are expressed at the ventral midline. Robo3 is a divergent member of the Robo family which instead of being a positive regulator of Slit responsiveness, antagonizes Slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit2 has been shown by surface plasmon resonance experiments and mutational analysis to be is the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804 182 PPYISKAKNTGVSVGQKGILSCEASAVPMAEFQWFKEETRLATGLDGMRIEnkgRM----STLTFFNV-----SEKDYGN 252
Cdd:cd07693    1 PRIVEHPSDLIVSKGDPATLNCKAEGRPTPTIQWLKNGQPLETDKDDPRSH---RIvlpsGSLFFLRVvhgrkGRSDEGV 77

                         90
                 ....*....|....*....
gi 981220804 253 YTCVATNKLGNT---NASI 268
Cdd:cd07693   78 YVCVAHNSLGEAvsrNASL 96

Third immunoglobulin (Ig) domain of contactin; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the third immunoglobulin (Ig) domain of contactins. Contactins are neural cell adhesion molecules and are comprised of six Ig domains followed by four fibronectin type III (FnIII) domains anchored to the membrane by glycosylphosphatidylinositol. The first four Ig domains form the intermolecular binding fragment, which arranges as a compact U-shaped module via contacts between Ig domains 1 and 4, and between Ig domains 2 and 3. Contactin-2 (TAG-1, axonin-1) may play a part in the neuronal processes of neurite outgrowth, axon guidance and fasciculation, and neuronal migration. This group also includes contactin-1 and contactin-5. The different contactins show different expression patterns in the central nervous system. During development and in adulthood, contactin-2 is transiently expressed in subsets of central and peripheral neurons. Contactin-5 is expressed specifically in the rat postnatal nervous system, peaking at about 3 weeks postnatal, and a lack of contactin-5 (NB-2) results in an impairment of neuronal activity in the rat auditory system. Contactin-5 is highly expressed in the adult human brain in the occipital lobe and in the amygdala. Contactin-1 is differentially expressed in tumor tissues and may, through a RhoA mechanism, facilitate invasion and metastasis of human lung adenocarcinoma. This group belongs to the I-set of IgSF domains.

                         10        20        30        40        50
                 ....*....|....*....|....*....|....*....|....*....|....*....
gi 981220804 109 GSSVTLLCLAIGRPEPTVTWRHL--SVKEGQGFVSEDEYLEISDIKRDQSGEYECSALN 165
Cdd:cd04968   16 GQTVTLECFALGNPVPQIKWRKVdgSPSSQWEITTSEPVLEIPNVQFEDEGTYECEAEN 74

Immunoglobulin domain of human Synaptic Adhesion-Like Molecule 5 (SALM5) and similar proteins; member of the I-set of IgSF domains; This group contains the immunoglobulin domain of human Synaptic Adhesion-Like Molecule 5 (SALM5) and similar proteins. The SALM (for synaptic adhesion-like molecules; also known as Lrfn for leucine-rich repeat and fibronectin type III domain containing) family of adhesion molecules consists of five known members: SALM1/Lrfn2, SALM2/Lrfn1, SALM3/Lrfn4, SALM4/Lrfn3, and SALM5/Lrfn5. SALMs share a similar domain structure, containing leucine-rich repeats (LRRs), an immunoglobulin (Ig) domain, and a fibronectin III (FNIII) domain, followed by a transmembrane domain and a C-terminal PDZ-binding motif. SALM5 is implicated in autism spectrum disorders (ASDs) and schizophrenia, induces presynaptic differentiation in contacting axons. SALM5 interacts with the Ig domains of LAR (Leukocyte common Antigen-Related) family receptor protein tyrosine phosphatases (LAR-RPTPs; LAR, PTPdelta, and PTPsigma). In addition, PTPdelta is implicated in ASDs, ADHD, bipolar disorder, and restless leg syndrome. Studies have shown that LAR-RPTPs are novel and splicing-dependent presynaptic ligands for SALM5, and that they mediate SALM5-dependent presynaptic differentiation. Furthermore, SALM5 maintains AMPA receptor (AMPAR)-mediated excitatory synaptic transmission through mechanisms involving the interaction of SALM5 with LAR-RPTPs. This group belongs to the I-set of immunoglobulin superfamily (IgSF) domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 981220804 196 GQKGILSCEASAVPMAEFQWFKEETRLATGLDGMRIENKGrmsTLTFFNVSEKDYGNYTCVATNKLGNTNASITL 270
Cdd:cd05764   15 GQRATLRCKARGDPEPAIHWISPEGKLISNSSRTLVYDNG---TLDILITTVKDTGAFTCIASNPAGEATARVEL 86

Immunoglobulin domain; Members of the immunoglobulin superfamily are found in hundreds of proteins of different functions. Examples include antibodies, the giant muscle kinase titin and receptor tyrosine kinases. Immunoglobulin-like domains may be involved in protein-protein and protein-ligand interactions.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 981220804  100 ISSDITVNEGSSVTLLCLAI-GRPEPTVTWRhlsvKEGQGFVSEDEY-----------LEISDIKRDQSGEYECSALN 165
Cdd:pfam00047   2 APPTVTVLEGDSATLTCSAStGSPGPDVTWS----KEGGTLIESLKVkhdngrttqssLLISNVTKEDAGTYTCVVNN 75

Second immunoglobulin (Ig)-like domain in Robo (roundabout) receptors; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the second immunoglobulin (Ig)-like domain in Robo (roundabout) receptors. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of the Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, Robo2, and Robo3), and three mammalian Slit homologs (Slit-1,Slit-2, Slit-3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, Robo2, and Robo3 are expressed by commissural neurons in the vertebrate spinal cord and Slit-1, Slit-2, Slit-3 are expressed at the ventral midline. Robo-3 is a divergent member of the Robo family which instead of being a positive regulator of Slit responsiveness, antagonizes Slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit-2 has been shown by surface plasmon resonance experiments and mutational analysis to be the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804 102 SDITVNEGSSVTLLCLA-IGRPEPTVTWRhlsvKEGQGFVSEDEY--------LEISDIKRDQSGEYECSALNDVAAPDV 172
Cdd:cd05724    5 SDTQVAVGEMAVLECSPpRGHPEPTVSWR----KDGQPLNLDNERvrivddgnLLIAEARKSDEGTYKCVATNMVGERES 80

                 ....*..
gi 981220804 173 RKVKITV 179
Cdd:cd05724   81 RAARLSV 87

Fourth Ig domain of the neural cell adhesion molecule contactin-2, and similar domains; The members here are composed of the fourth Ig domain of the neural cell adhesion molecule contactin-2. Contactins are comprised of six Ig domains followed by four fibronectin type III (FnIII) domains anchored to the membrane by glycosylphosphatidylinositol. Contactin-2 (also called TAG-1, axonin-1) facilitates cell adhesion by homophilic binding between molecules in apposed membranes. The first four Ig domains form the intermolecular binding fragment which arranges as a compact U-shaped module by contacts between Ig domains 1 and 4, and domains 2 and 3. It has been proposed that a linear zipper-like array forms, from contactin-2 molecules alternatively provided by the two apposed membranes.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 981220804 184 YISKAKNTGVSVGQKGILSCEASAVPMAEFQWFKEETRLATgldGMRIENKGrmSTLTFFNVSEKDYGNYTCVATNKLGN 263
Cdd:cd05728    2 WLKVISDTEADIGSSLRWECKASGNPRPAYRWLKNGQPLAS---ENRIEVEA--GDLRITKLSLSDSGMYQCVAENKHGT 76

                 ....*..
gi 981220804 264 TNASITL 270
Cdd:cd05728   77 IYASAEL 83