Immunoglobulin (Ig)-like domain of human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) domains 2, 4, and 6, and similar domains; The members here are composed of the second, fourth, and sixth immunoglobulin (Ig)-like domains in human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) protein subfamily. The CEA family is a group of anchored or secreted glycoproteins expressed by epithelial cells, leukocytes, endothelial cells, and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. This group represents the CEACAM subfamily. CEACAM1 has many important cellular functions; it is a cell adhesion molecule and a signaling molecule that regulates the growth of tumor cells, an angiogenic factor, and a receptor for bacterial and viral pathogens, including mouse hepatitis virus (MHV). In mice, four isoforms of CEACAM1 generated by alternative splicing have either two [D1, D4] or four [D1-D4] Ig-like domains on the cell surface.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 85719313 146 QPFLQVTN-TTVKELDSVTLTCLSNDIGANIQWLFNSQSLQLTERMTLSQNNSILRIDPIKREDAGEYQCEISNPVSVRR 224
Cdd:cd05740   1 KPFISSNNsNPVEDKDAVTLTCEPETQNTSYLWWFNGQSLPVTPRLTLSNGNRTLTLLNVTREDAGAYQCEISNPVSANR 80

                ....*....
gi 85719313 225 SNSIKLDII 233
Cdd:cd05740  81 SDPVTLDVI 89

Immunoglobulin (Ig)-like domain of human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) domains 2, 4, and 6, and similar domains; The members here are composed of the second, fourth, and sixth immunoglobulin (Ig)-like domains in human carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) protein subfamily. The CEA family is a group of anchored or secreted glycoproteins expressed by epithelial cells, leukocytes, endothelial cells, and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. This group represents the CEACAM subfamily. CEACAM1 has many important cellular functions; it is a cell adhesion molecule and a signaling molecule that regulates the growth of tumor cells, an angiogenic factor, and a receptor for bacterial and viral pathogens, including mouse hepatitis virus (MHV). In mice, four isoforms of CEACAM1 generated by alternative splicing have either two [D1, D4] or four [D1-D4] Ig-like domains on the cell surface.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 85719313 146 QPFLQVTN-TTVKELDSVTLTCLSNDIGANIQWLFNSQSLQLTERMTLSQNNSILRIDPIKREDAGEYQCEISNPVSVRR 224
Cdd:cd05740   1 KPFISSNNsNPVEDKDAVTLTCEPETQNTSYLWWFNGQSLPVTPRLTLSNGNRTLTLLNVTREDAGAYQCEISNPVSANR 80

                ....*....
gi 85719313 225 SNSIKLDII 233
Cdd:cd05740  81 SDPVTLDVI 89

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 85719313   152 TNTTVKELDSVTLTCLSNDIG-ANIQWLFNSQSL--QLTERMTLSQNNSILRIDPIKREDAGEYQCEISN 218
Cdd:pfam13927   9 SSVTVREGETVTLTCEATGSPpPTITWYKNGEPIssGSTRSRSLSGSNSTLTISNVTRSDAGTYTCVASN 78

IL-1 receptor-like protein; Provisional

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 85719313   67 WYKGNTTAidkeiarFVPNSNMNFTGQAYSGREIIYSNGSLLFQMITMKDMGVYTLDMTDENyRRTQATVRFHVHQpvtq 146
Cdd:PHA02826  67 WSKTDSLA-------FVRDSGARTKIKKITHNEIGDRSENLWIGNVINIDEGIYICTISSGN-ICEESTIRLTFDS---- 134

                         90       100       110       120       130       140       150
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 85719313  147 pflQVTNTTVKELDSVTLTCLSNDIGAN------IQWLFNSQSLQLTERMTLSQNNSILRIDPIKREDAGEYQCEI 216
Cdd:PHA02826 135 ---GTINYQFNSGKDSKLHCYGTDGISStfkdytLTWYKNGNIVLYTDRIQLRNNNSTLVIKSATHDDSGIYTCNL 207

Immunoglobulin (Ig)-like domain of carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) and similar proteins; The members here are composed of the immunoglobulin (Ig)-like domain in carcinoembryonic antigen (CEA) related cell adhesion molecule (CEACAM) and related domains. The CEA family is a group of anchored or secreted glycoproteins, expressed by epithelial cells, leukocytes, endothelial cells and placenta. The CEA family is divided into the CEACAM and pregnancy-specific glycoprotein (PSG) subfamilies. This group represents the CEACAM subfamily. CEACAM1 has many important cellular functions: it is a cell adhesion molecule and a signaling molecule that regulates the growth of tumor cells, an angiogenic factor, and a receptor for bacterial and viral pathogens, including mouse hepatitis virus (MHV). In mice, four isoforms of CEACAM1 generated by alternative splicing have either two (D1, D4) or four (D1-D4) Ig-like domains on the cell surface. This family corresponds to the D1 Ig-like domain. Also belonging to this group is the N-terminal immunoglobulin (Ig)-like domain of the signaling lymphocyte activation molecule (SLAM) family, CD84-like family. The SLAM family is a group of immune-cell specific receptors that can regulate both adaptive and innate immune responses. SLAM family proteins are organized as an extracellular domain with having two or four Ig-like domains, a single transmembrane segment, and a cytoplasmic region having Tyr-based motifs. The extracellular domain is organized as a membrane-distal Ig variable (IgV) domain that is responsible for ligand recognition and a membrane-proximal truncated Ig constant-2 (IgC2) domain.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 85719313  43 PQVAEDNNVLLLVHNLPLALGAFAWYKGNTTAIDKEIARFVPNSNMNFTGQAYSGREIIYSNGSLLFQMITMKDMGVYTL 122
Cdd:cd05741   5 FYGAEGKNVLLLVPNLQTPLKSVSWYKGKQVSRNDEIAEYENSSDEFRAGSAFSGREYIYTNGSLLIQNITLSDTGFYTL 84

                        90
                ....*....|....*...
gi 85719313 123 DMTDENYRRTQATVRFHV 140
Cdd:cd05741  85 ESTNIGGKTESATFQLHV 102

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 85719313    38 IEAVPPQVAEDNNVLLLVHNLPL---ALGAFAWYKGNT-TAIDKEIARFVPNSNMNFTGQAYSGRE-IIYSNGSLLFQMI 112
Cdd:pfam07686   1 QTPREVTVALGGSVTLPCTYSSSmseASTSVYWYRQPPgKGPTFLIAYYSNGSEEGVKKGRFSGRGdPSNGDGSLTIQNL 80

                          90       100
                  ....*....|....*....|....*....
gi 85719313   113 TMKDMGVYTLDMTDENYRRTQATVRFHVH 141
Cdd:pfam07686  81 TLSDSGTYTCAVIPSGEGVFGKGTRLTVL 109

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 85719313   152 TNTTVKELDSVTLTCLSNDIG-ANIQWLFNSQSL--QLTERMTLSQNNSILRIDPIKREDAGEYQCEISN 218
Cdd:pfam13927   9 SSVTVREGETVTLTCEATGSPpPTITWYKNGEPIssGSTRSRSLSGSNSTLTISNVTRSDAGTYTCVASN 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 85719313   152 TNTTVKELDSVTLTCLSNDI--GANIQWLFNSQSLQLTERMTLSQNNSI---LRIDPIKREDAGEYQCEISNPVSVRRSN 226
Cdd:pfam00047   4 PTVTVLEGDSATLTCSASTGspGPDVTWSKEGGTLIESLKVKHDNGRTTqssLLISNVTKEDAGTYTCVVNNPGGSATLS 83

                  ..
gi 85719313   227 SI 228
Cdd:pfam00047  84 TS 85

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
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 85719313 152 TNTTVKELDSVTLTC-LSNDIGANIQWLFNSQSLQ-LTERMTLSQNnsILRIDPIKREDAGEYQCEISN 218
Cdd:cd20978   9 KNVVVKGGQDVTLPCqVTGVPQPKITWLHNGKPLQgPMERATVEDG--TLTIINVQPEDTGYYGCVATN 75

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 85719313 146 QP-FLQVTNTTVKELDSVTLTC-LSNDIGANIQWLFNSQSLQLTE-----RMTLSQNN--SILRIDPIKREDAGEYQCEI 216
Cdd:cd05732   2 QPkITYLENQTAVELEQITLTCeAEGDPIPEITWRRATRGISFEEgdldgRIVVRGHArvSSLTLKDVQLTDAGRYDCEA 81

                        90
                ....*....|....*.
gi 85719313 217 SNPVSVrRSNSIKLDI 232
Cdd:cd05732  82 SNRIGG-DQQSMYLEV 96

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 85719313 143 PVTQPFLQVTNTTVKELDSVTLTCL-SNDIGANIQWLFNSQSLQ-LTERMTLSQNNSILRIDPIKREDAGEYQCEISNPV 220
Cdd:cd20970   1 PVISTPQPSFTVTAREGENATFMCRaEGSPEPEISWTRNGNLIIeFNTRYIVRENGTTLTIRNIRRSDMGIYLCIASNGV 80

                        90
                ....*....|..
gi 85719313 221 SVRRSNSIKLDI 232
Cdd:cd20970  81 PGSVEKRITLQV 92

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
                ....*....|....*....|....*....|....*....|....*....|....*....|.
gi 85719313 174 NIQWLFNSQSLQLTE--RMTLSQNNsiLRIDPIKREDAGEYQCEISNPVSVRRSNSIKLDI 232
Cdd:cd05724  29 TVSWRKDGQPLNLDNerVRIVDDGN--LLIAEARKSDEGTYKCVATNMVGERESRAARLSV 87

agrin-responsive second immunoglobulin-like domains (Ig2) of the Muscle-specific kinase (MuSK) ectodomain; a member of the I-set of Ig superfamily domains; The members here are composed of the second immunoglobulin-like (Ig) domains of the Muscle-specific kinase (MuSK) ectodomain. 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 85719313 152 TNTTVKELDSVTLTCLS-NDIGANIQWLFNSQSLQLTERMTLSQNNSiLRIDPIKREDAGEYQCEISNPVSVRRSNSIKL 230
Cdd:cd20968   7 TNVTIIEGLKAVLPCTTmGNPKPSVSWIKGDDLIKENNRIAVLESGS-LRIHNVQKEDAGQYRCVAKNSLGIAYSKPVTI 85

                ..
gi 85719313 231 DI 232
Cdd:cd20968  86 EV 87

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        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 85719313 152 TNTTVKELDSVTLTC-LSNDIGANIQWLFNSQSL-QLTERMTLSQNNSI-LRIDPIKREDAGEYQCEISNpvsvrrSNSI 228
Cdd:cd20949   7 YVTTVKEGQSATILCeVKGEPQPNVTWHFNGQPIsASVADMSKYRILADgLLINKVTQDDTGEYTCRAYQ------VNSI 80

                ....*.
gi 85719313 229 KLDIIF 234
Cdd:cd20949  81 ASDMQE 86

Third immunoglobulin domain of the Drosophila melanogaster Dscam protein, and similar domains; a member of the Constant 2 (C2)-set of IgSF domains; The members here are composed of the third 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. 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. This group belongs to the C2-set of IgSF domains, having A, B, and E strands in one beta-sheet and A', G, F, C, and C' in the other. Unlike other Ig domain sets, the C2-set lacks the D strand.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|....*....
gi 85719313 163 TLTCLSNDIGA-NIQWLFNSQSLQLTERMTLSQNNsILRIDPIKREDAGEYQCEISNPV 220
Cdd:cd20957  20 VFNCSVTGNPIhTVLWMKDGKPLGHSSRVQILSED-VLVIPSVKREDKGMYQCFVRNDG 77

First immunoglobulin (Ig) domain of contactin-2; member of the I-set of Ig superfamily domains; The members here are composed of the first immunoglobulin (Ig) domain of the neural cell adhesion molecule contactin-2-like. Contactins are comprised of six Ig domains followed by four fibronectin type III (FnIII) domains anchored to the membrane by glycosylphosphatidylinositol. Contactin-2 (TAG-1, axonin-1) facilitates cell adhesion by homophilic binding between molecules in apposed membranes. It may play a part in the neuronal processes of neurite outgrowth, axon guidance and fasciculation, and neuronal migration. 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. 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-2 is also expressed in retinal amacrine cells in the developing chick retina, corresponding to the period of formation and maturation of AC processes. This group belongs to the I-set of IgSF domains.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|...
gi 85719313 162 VTLTCLSN-DIGANIQWLFNSQSLQLTE--RMTLSQNNSILRiDPIKREDAGEYQCEISNPVS--VRRSNSIK 229
Cdd:cd05850  23 VTLACRARaSPPATYRWKMNGTELKMEPdsRYRLVAGNLVIS-NPVKAKDAGSYQCLASNRRGtvVSREASLR 94

T-cell surface glycoprotein CD3 delta chain; This is an immunoglobulin-like domain. It is found on the T-cell surface glycoprotein CD3 delta chain. CD3delta and CD3epsilon complex together as part of the T-cell receptor complex.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|..
gi 85719313   160 DSVTLTCLSNDigANIQWLFNSQSLQLTERMTLSQNNSILridpikrEDAGEYQCEISNPVS 221
Cdd:pfam16680   2 GKVLLTCNSSS--KSITWLKDGKGIKSTNTKTLDLGKFSE-------DPRGLYQCQGEKKKS 54

N-terminal immunoglobulin (Ig)-like domain of T-cell surface antigen CD2, and similar domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain (or domain 1) of T-cell surface antigen Clusters of Differentiation (CD) 2 and similar proteins. CD2 is a T-cell specific surface glycoprotein and is critically important for mediating adhesion between T cells and antigen-presenting cells or between cytolytic T cells and target cells. CD2 is located on chromosome 1 at 1p13 in humans and on chromosome 3 in mice. CD2 contains an extracellular domain with two or Ig-like domains, a single transmembrane segment, and a cytoplasmic region rich in proline and basic residues.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 85719313  46 AEDNNVLLLVHNLPLALGAFAWYKGNttaidKEIARFVPNSNMNFTGqAYSGR-EIIYSNGSLLFQMITMKDMGVYTLDM 124
Cdd:cd05775   8 ALGGNVTLTISSLQDDIDEIKWKKTK-----DKIVEWENNIGPTYFG-SFKDRvLLDKESGSLTIKNLTKEDSGTYELEI 81

                        90
                ....*....|....*..
gi 85719313 125 TDENYRRTQATVRFHVH 141
Cdd:cd05775  82 TSTNGKVLSSKFTLEVL 98

Third immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM), and similar domains; The members here are composed of the third immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM). L1 belongs to the L1 subfamily of cell adhesion molecules (CAMs) and is comprised of an extracellular region having six Ig-like domains and five fibronectin type III domains, a transmembrane region and an intracellular domain. L1 is primarily expressed in the nervous system and is involved in its development and function. L1 is associated with an X-linked recessive disorder, X-linked hydrocephalus, MASA syndrome, and spastic paraplegia type 1, that involves abnormalities of axonal growth. This group also contains the chicken neuron-glia cell adhesion molecule, Ng-CAM and human neurofascin.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 85719313 152 TNTTVKELDSVTLTCLSNDIGA-NIQWLFNSQSLqLTERMTLSQNNSILRIDPIKREDAGEYQCEISNPV 220
Cdd:cd05731   3 SSTMVLRGGVLLLECIAEGLPTpDIRWIKLGGEL-PKGRTKFENFNKTLKIENVSEADSGEYQCTASNTM 71