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 1622895094 148 PDVYIPETLEPGQPVTVVCVFNWAfeeCPA--PSFSWTGTALSSQGT-------KPTTYHFSVLSFTPSPQDHDTDLTCH 218
Cdd:cd20987     1 PNIHVPEELEAGQEVTLTCSVPDN---CPAlsPEFSWLGAALTPLPPvlgrleeEGTTTHSSVLTFTPRPEDHGTNLTCQ 77

                          90
                  ....*....|....*..
gi 1622895094 219 VDFSRKGVSAQRTVRLR 235
Cdd:cd20987    78 VKFPGATVTTERTIQLN 94

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 1622895094 263 VPYLEAQKGQFLRLLCAADSQPPATLSWVLQDRVLSLSHPwgprtlgLELPGVKAGDSGHYTCRAENRLGSQQRALDLSV 342
Cdd:cd20948     2 PSDTYYLSGENLNLSCHAASNPPAQYSWTINGTFQTSSQE-------LFLPAITENNEGTYTCSAHNSLTGKNISLVLSV 74

                  ..
gi 1622895094 343 QY 344
Cdd:cd20948    75 TV 76

Second immunoglobulin domain of Cluster of Differentiation (CD) 33 and related Siglecs; member of the C2-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig) domain of Cluster of Differentiation (CD) 33 (also known as sialic-acid binding immunoglobulin type-lectin 3 (Siglec-3)) and related Siglecs. CD33, a Siglec family member, is a well-known immunotherapeutic target in acute myeloid leukemia (AML). It is an inhibitory sialoadhesin expressed in human leukocytes of the myeloid lineage and some lymphoid subsets, including natural killer (NK) cells. Siglecs are primarily expressed on immune cells and recognize sialic acid-containing glycan ligands. Siglecs are organized as an extracellular module composed of Ig-like domains (an N-terminal variable set of Ig-like carbohydrate recognition domains, and 1 to 16 constant Ig-like domains), followed by transmembrane and short cytoplasmic domains. Human Siglecs are classified into two subgroups, one subgroup is comprised of sialoadhesin (Siglec-1), CD22 (Siglec-2), and MAG (Siglec-4, myelin-associated glycoprotein), the other subgroup is comprised of CD33-related Siglecs which include CD33 (Siglec-3) and human Siglecs 5-11. CD33 (Siglec-3) is the smallest Siglec member. It preferentially binds to alpha2-6- and alpha2-3-sialylated glycans and strongly binds to sialylated ligands on leukemic cell lines. 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. This group includes CD33-related Siglecs which belong to the C2-set of IgSF domains. Unlike the C1-set, the C2-set structures do not have a D strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1622895094 148 PDVYIPETLEPGQPVTVVCVFNWAfeeCPA--PSFSWTGTALSSQGT-------KPTTYHFSVLSFTPSPQDHDTDLTCH 218
Cdd:cd20987     1 PNIHVPEELEAGQEVTLTCSVPDN---CPAlsPEFSWLGAALTPLPPvlgrleeEGTTTHSSVLTFTPRPEDHGTNLTCQ 77

                          90
                  ....*....|....*..
gi 1622895094 219 VDFSRKGVSAQRTVRLR 235
Cdd:cd20987    78 VKFPGATVTTERTIQLN 94

Fifth immunoglobulin (Ig)-like domain of the carcinoembryonic antigen (CEA) related cell adhesion molecule 5 (CEACAM5) and similar domains; member of the C2-set IgSF domains; The members here are composed of the fifth immunoglobulin (Ig)-like domain of the carcinoembryonic antigen (CEA) related cell adhesion molecule 5 (CEACAM5) and similar 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. Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5), also known as CD66e (Cluster of Differentiation 66e), is a cell surface glycoprotein that plays a role in cell adhesion, intracellular signaling and tumor progression. Diseases associated with CEACAM5 include lung cancer and rectum cancer. 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' in the other. Unlike other Ig domain sets, the C2-set lacks the D strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1622895094 263 VPYLEAQKGQFLRLLCAADSQPPATLSWVLQDRVLSLSHPwgprtlgLELPGVKAGDSGHYTCRAENRLGSQQRALDLSV 342
Cdd:cd20948     2 PSDTYYLSGENLNLSCHAASNPPAQYSWTINGTFQTSSQE-------LFLPAITENNEGTYTCSAHNSLTGKNISLVLSV 74

                  ..
gi 1622895094 343 QY 344
Cdd:cd20948    75 TV 76

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1622895094  264 PYLEAQKGQFLRLLCAADSQPPATLSWVLQDRVLSLSHP-----WGPRTLGLELPGVKAGDSGHYTCRAENRLGSQQRAL 338
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGSPPPEVTWYKQGGKLLAESGrfsvsRSGSTSTLTISNVTPEDSGTYTCAATNSSGSASSGT 81

                   ....
gi 1622895094  339 DLSV 342
Cdd:smart00410  82 TLTV 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 1622895094  25 VEKLVMVQEGLCVSVSCSFnypSRGWTESTPAYgYWFKagTETETSKDAPVATNNQNREVEmSTQGRFQLTGDPGKKSCS 104
Cdd:pfam07686   2 TPREVTVALGGSVTLPCTY---SSSMSEASTSV-YWYR--QPPGKGPTFLIAYYSNGSEEG-VKKGRFSGRGDPSNGDGS 74

                          90       100       110
                  ....*....|....*....|....*....|....*...
gi 1622895094 105 LVIRDAQMWDEARYFFRVergTYVRYNFMNNGFLLKVT 142
Cdd:pfam07686  75 LTIQNLTLSDSGTYTCAV---IPSGEGVFGKGTRLTVL 109

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1622895094   29 VMVQEGLCVSVSCSFNYPSrgwtestPAYGYWFKagtetetskdapvatnnqNREVEMSTQGRFQLTGDPGkkSCSLVIR 108
Cdd:smart00410   4 VTVKEGESVTLSCEASGSP-------PPEVTWYK------------------QGGKLLAESGRFSVSRSGS--TSTLTIS 56

                           90
                   ....*....|....*
gi 1622895094  109 DAQMWDEARYFFRVE 123
Cdd:smart00410  57 NVTPEDSGTYTCAAT 71

Second immunoglobulin domain of Cluster of Differentiation (CD) 33 and related Siglecs; member of the C2-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig) domain of Cluster of Differentiation (CD) 33 (also known as sialic-acid binding immunoglobulin type-lectin 3 (Siglec-3)) and related Siglecs. CD33, a Siglec family member, is a well-known immunotherapeutic target in acute myeloid leukemia (AML). It is an inhibitory sialoadhesin expressed in human leukocytes of the myeloid lineage and some lymphoid subsets, including natural killer (NK) cells. Siglecs are primarily expressed on immune cells and recognize sialic acid-containing glycan ligands. Siglecs are organized as an extracellular module composed of Ig-like domains (an N-terminal variable set of Ig-like carbohydrate recognition domains, and 1 to 16 constant Ig-like domains), followed by transmembrane and short cytoplasmic domains. Human Siglecs are classified into two subgroups, one subgroup is comprised of sialoadhesin (Siglec-1), CD22 (Siglec-2), and MAG (Siglec-4, myelin-associated glycoprotein), the other subgroup is comprised of CD33-related Siglecs which include CD33 (Siglec-3) and human Siglecs 5-11. CD33 (Siglec-3) is the smallest Siglec member. It preferentially binds to alpha2-6- and alpha2-3-sialylated glycans and strongly binds to sialylated ligands on leukemic cell lines. 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. This group includes CD33-related Siglecs which belong to the C2-set of IgSF domains. Unlike the C1-set, the C2-set structures do not have a D strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1622895094 148 PDVYIPETLEPGQPVTVVCVFNWAfeeCPA--PSFSWTGTALSSQGT-------KPTTYHFSVLSFTPSPQDHDTDLTCH 218
Cdd:cd20987     1 PNIHVPEELEAGQEVTLTCSVPDN---CPAlsPEFSWLGAALTPLPPvlgrleeEGTTTHSSVLTFTPRPEDHGTNLTCQ 77

                          90
                  ....*....|....*..
gi 1622895094 219 VDFSRKGVSAQRTVRLR 235
Cdd:cd20987    78 VKFPGATVTTERTIQLN 94

Fifth immunoglobulin (Ig)-like domain of the carcinoembryonic antigen (CEA) related cell adhesion molecule 5 (CEACAM5) and similar domains; member of the C2-set IgSF domains; The members here are composed of the fifth immunoglobulin (Ig)-like domain of the carcinoembryonic antigen (CEA) related cell adhesion molecule 5 (CEACAM5) and similar 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. Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5), also known as CD66e (Cluster of Differentiation 66e), is a cell surface glycoprotein that plays a role in cell adhesion, intracellular signaling and tumor progression. Diseases associated with CEACAM5 include lung cancer and rectum cancer. 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' in the other. Unlike other Ig domain sets, the C2-set lacks the D strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1622895094 263 VPYLEAQKGQFLRLLCAADSQPPATLSWVLQDRVLSLSHPwgprtlgLELPGVKAGDSGHYTCRAENRLGSQQRALDLSV 342
Cdd:cd20948     2 PSDTYYLSGENLNLSCHAASNPPAQYSWTINGTFQTSSQE-------LFLPAITENNEGTYTCSAHNSLTGKNISLVLSV 74

                  ..
gi 1622895094 343 QY 344
Cdd:cd20948    75 TV 76

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1622895094  264 PYLEAQKGQFLRLLCAADSQPPATLSWVLQDRVLSLSHP-----WGPRTLGLELPGVKAGDSGHYTCRAENRLGSQQRAL 338
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGSPPPEVTWYKQGGKLLAESGrfsvsRSGSTSTLTISNVTPEDSGTYTCAATNSSGSASSGT 81

                   ....
gi 1622895094  339 DLSV 342
Cdd:smart00410  82 TLTV 85

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1622895094 368 TSLPVLEGQSLRLVCVTHSSPPARLSWTQGGQTVGSSQPSDP------GVLELPRVQVEQEGEFTCHA 429
Cdd:pfam13927   9 SSVTVREGETVTLTCEATGSPPPTITWYKNGEPISSGSTRSRslsgsnSTLTISNVTRSDAGTYTCVA 76

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1622895094 372 VLEGQSLRLVCVTHSSPPARLSWTQGGQTVGSSQ------PSDPGVLELPRVQVEQEGEFTCHAQHPLGSQHVSLSLSV 444
Cdd:pfam07679  12 VQEGESARFTCTVTGTPDPEVSWFKDGQPLRSSDrfkvtyEGGTYTLTISNVQPDDSGKYTCVATNSAGEAEASAELTV 90

Third immunoglobulin (Ig)-like domain of peroxidasin; The members here are composed of the third immunoglobulin (Ig)-like domain in peroxidasin. Peroxidasin has a peroxidase domain and interacting extracellular motifs containing four Ig-like domains. It has been suggested that peroxidasin is secreted and has functions related to the stabilization of the extracellular matrix. It may play a part in various other important processes such as removal and destruction of cells which have undergone programmed cell death and protection of the organism against non-self.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 1622895094 374 EGQSLRLVCVTHSSPPARLSWTQGGQTVG---SSQPSDPGVLELPRVQVEQEGEFTCHAQHPLGSQHVSLSLSV 444
Cdd:cd05745     1 EGQTVDFLCEAQGYPQPVIAWTKGGSQLSvdrRHLVLSSGTLRISRVALHDQGQYECQAVNIVGSQRTVAQLTV 74

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 1622895094 368 TSLPVLEGQSLRLVC-VTHSSPPARLSWTQGGQTVGSSQPSDPG-------VLELPRVQVEQEGEFTCHAQHPLGSQHVS 439
Cdd:pfam00047   4 PTVTVLEGDSATLTCsASTGSPGPDVTWSKEGGTLIESLKVKHDngrttqsSLLISNVTKEDAGTYTCVVNNPGGSATLS 83

                  ...
gi 1622895094 440 LSL 442
Cdd:pfam00047  84 TSL 86

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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 1622895094 378 LRLVCVTHSSPPARLSWTQGGQTVGSSQPSDP------GVLELPRVQVEQEGEFTCHAQHPLGSQ 436
Cdd:cd00096     1 VTLTCSASGNPPPTITWYKNGKPLPPSSRDSRrselgnGTLTISNVTLEDSGTYTCVASNSAGGS 65

Sixth 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 sixth 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 1622895094 268 AQKGQFLRLLCA-ADSQPPATLSWVLQDRVLSLSHPW-----GPRTLGLELPGVKAGDSGHYTCRAENRLGSQQRALDLS 341
Cdd:cd20959    14 AQVGMRAQLHCGvPGGDLPLNIRWTLDGQPISDDLGItvsrlGRRSSILSIDSLEASHAGNYTCHARNSAGSASYTAPLT 93

                  .
gi 1622895094 342 V 342
Cdd:cd20959    94 V 94

Immunoglobulin (Ig)-like domain of human titin C terminus and similar proteins; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the fifth immunoglobulin (Ig)-like domain from the C-terminus of human titin x and similar proteins. Titin (also called connectin) is a fibrous sarcomeric protein specifically found in vertebrate striated muscle. Titin is gigantic; depending on isoform composition it ranges from 2970 to 3700 kDa, and is of a length that spans half a sarcomere. Titin largely consists of multiple repeats of Ig-like and fibronectin type 3 (FN-III)-like domains. Titin connects the ends of myosin thick filaments to Z disks and extends along the thick filament to the H zone and appears to function similar to an elastic band, keeping the myosin filaments centered in the sarcomere during muscle contraction or stretching. 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 1622895094 369 SLPVLEGQSLRLVCVTHSSPPARLSWTQGGQTVGSSQ------PSDPGVLELPRVQVEQEGEFTCHAQHPLGSQHVSLSL 442
Cdd:cd05747    12 SLTVSEGESARFSCDVDGEPAPTVTWMREGQIIVSSQrhqitsTEYKSTFEISKVQMSDEGNYTVVVENSEGKQEAQFTL 91

                  .
gi 1622895094 443 S 443
Cdd:cd05747    92 T 92

Third immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM); 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, 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, or spastic paraplegia type 1, that involves abnormalities of axonal growth. This group also contains the chicken neuron-glia cell adhesion molecule, Ng-CAM.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1622895094 268 AQKGQFLRLLCAADSQPPATLSW------VLQDRVLSLSHPwgpRTLglELPGVKAGDSGHYTCRAENRLGSQQRALDLS 341
Cdd:cd05876     7 ALRGQSLVLECIAEGLPTPTVKWlrpsgpLPPDRVKYQNHN---KTL--QLLNVGESDDGEYVCLAENSLGSARHAYYVT 81

                  ..
gi 1622895094 342 VQ 343
Cdd:cd05876    82 VE 83

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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 1622895094 271 GQFLRLLCAADSQPPATLSWVLQDRVLSLS--HPWGPRTLglELPGVKAGDSGHYTCRAENRLGS 333
Cdd:cd05725    12 DDSAEFQCEVGGDPVPTVRWRKEDGELPKGryEILDDHSL--KIRKVTAGDMGSYTCVAENMVGK 74

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        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1622895094 368 TSLPVLEGQSLRLVCVTHSSPPARLSWTQggqtVGSSQPSDPG-------VLELPRVQVEQEGEFTCHAQHPLGSQHVSL 440
Cdd:cd05731     3 SSTMVLRGGVLLLECIAEGLPTPDIRWIK----LGGELPKGRTkfenfnkTLKIENVSEADSGEYQCTASNTMGSARHTI 78

                  ....
gi 1622895094 441 SLSV 444
Cdd:cd05731    79 SVTV 82

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.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1622895094 369 SLPVLEGQSLRLVCVTHSSPPARLSW--TQGGQTVGSSQPSDPGVLELPRVQVEQEGEFTCHAQHPLGSQHVSLSLSVH 445
Cdd:cd04968    10 DTYALKGQTVTLECFALGNPVPQIKWrkVDGSPSSQWEITTSEPVLEIPNVQFEDEGTYECEAENSRGKDTVQGRIIVQ 88

Fifth Ig-like domain of Roundabout (Robo) homolog 1/2, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fifth Ig-like domain of Roundabout (Robo) homolog 1/2 and similar domains. 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, -2, and -3), and three mammalian Slit homologs (Slit-1,-2, -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, -2, and -3 are expressed by commissural neurons in the vertebrate spinal cord and Slits 1, -2, -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 is the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site. The fifth Ig-like domain of Robo 1 and 2 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. 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

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1622895094 371 PVLEGQSLRLVCVTHSSPPARLSWTQGGQTVGSSQPS----DPGVLELPRVQVEQEGEFTCHAQHPLGSQHVSLSLSV 444
Cdd:cd20952    10 TVAVGGTVVLNCQATGEPVPTISWLKDGVPLLGKDERittlENGSLQIKGAEKSDTGEYTCVALNLSGEATWSAVLDV 87

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.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1622895094 268 AQKGQFLRLLCAADSQPPATLSWVLQDRVLSLSHPwgpRTL----GLELPGVKAGDSGHYTCRAENRLGSQQRALDLSV 342
Cdd:cd20978    13 VKGGQDVTLPCQVTGVPQPKITWLHNGKPLQGPME---RATvedgTLTIINVQPEDTGYYGCVATNEIGDIYTETLLHV 88

Second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor, and similar domains; member of the I-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor. FGF receptors bind FGF signaling polypeptides. FGFs participate in multiple processes such as morphogenesis, development, and angiogenesis. FGFs bind to four FGF receptor tyrosine kinases (FGFR1, FGFR2, FGFR3, FGFR4). Receptor diversity is controlled by alternative splicing producing splice variants with different ligand binding characteristics and different expression patterns. FGFRs have an extracellular region comprised of three Ig-like domains, a single transmembrane helix, and an intracellular tyrosine kinase domain. Ligand binding and specificity reside in the Ig-like domains 2 and 3, and the linker region that connects these two. FGFR activation and signaling depend on FGF-induced dimerization, a process involving cell surface heparin or heparin sulfate proteoglycans. This group also contains fibroblast growth factor (FGF) receptor like-1(FGFRL1). FGFRL1 does not have a protein tyrosine kinase domain at its C-terminus; neither does its cytoplasmic domain appear to interact with a signaling partner. It has been suggested that FGFRL1 may not have any direct signaling function, but instead acts as a decoy receptor trapping FGFs and preventing them from binding other receptors.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 1622895094 274 LRLLCAADSQPPATLSWVLQDRVLSLSHPWGP-----RTLGLELPGVKAGDSGHYTCRAENRLGSQQRALDLSV 342
Cdd:cd05729    22 VRLECGAGGNPMPNITWLKDGKEFKKEHRIGGtkveeKGWSLIIERAIPRDKGKYTCIVENEYGSINHTYDVDV 95

C-terminal immunoglobulin (Ig)-like domain of myomesin and M-protein; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the C-terminal immunoglobulin (Ig)-like domain of myomesin and M-protein (also known as myomesin-2). Myomesin and M-protein are both structural proteins localized to the M-band, a transverse structure in the center of the sarcomere, and are candidates for M-band bridges. Both proteins are modular, consisting mainly of repetitive Ig-like and fibronectin type III (FnIII) domains. Myomesin is expressed in all types of vertebrate striated muscle; M-protein has a muscle-type specific expression pattern. Myomesin is present in both slow and fast fibers; M-protein is present only in fast fibers. It has been suggested that myomesin acts as a molecular spring with alternative splicing as a means of modifying its elasticity.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1622895094 269 QKGQFLRLLCAADSQPPATLSWVLQDRVLSLSHPW-----GPRTLGLELPGVKAGDSGHYTCRAENRLGSQQRALDLSV 342
Cdd:cd05737    14 MEGKTLNLTCNVWGDPPPEVSWLKNDQALAFLDHCnlkveAGRTVYFTINGVSSEDSGKYGLVVKNKYGSETSDVTVSV 92

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.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1622895094 258 QPQGNVpylEAQKGQFLRLLCAADSQPPATLSWVLQD-RVLSLSHPWGPRTLG--LELPGVKAGDSGHYTCRAENRL-GS 333
Cdd:cd20970     7 QPSFTV---TAREGENATFMCRAEGSPEPEISWTRNGnLIIEFNTRYIVRENGttLTIRNIRRSDMGIYLCIASNGVpGS 83

                  ....*....
gi 1622895094 334 QQRALDLSV 342
Cdd:cd20970    84 VEKRITLQV 92

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.

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gi 1622895094 267 EAQKGQFLRLLCAADSQPPA-TLSWVLQDRVLSLSHPW------GPRTLGLELPGVKAGDSGHYTCRAENRLG 332
Cdd:cd05750    10 TVQEGSKLVLKCEATSENPSpRYRWFKDGKELNRKRPKnikirnKKKNSELQINKAKLEDSGEYTCVVENILG 82

Immunoglobulin I-set domain of the Leucine-rich repeat and immunoglobin-like domain-containing protein 1 (Lingo-1); The members here are composed of the immunoglobulin I-set (IgI) domain of the Leucine-rich repeat and immunoglobin-like domain-containing protein 1 (Lingo-1). Human Lingo-1 is a central nervous system-specific transmembrane glycoprotein also known as LERN-1, which functions as a negative regulator of neuronal survival, axonal regeneration, and oligodendrocyte differentiation and myelination. Lingo-1 is a key component of the Nogo receptor signaling complex (RTN4R/NGFR) in RhoA activation responsible for some inhibition of axonal regeneration by myelin-associated factors. The ligand-binding ectodomain of human Lingo-1 contains a bimodular, kinked structure composed of leucine-rich repeat (LRR) and immunoglobulin (Ig)-like modules. Diseases associated with Lingo-1 include mental retardation, autosomal recessive 64 and essential tremor. 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 Lingo-1 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.

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gi 1622895094 271 GQFLRLLCAADSQPPATLSWVLQDRVLSLSHPWGPRTL----GLELPGVKAGDSGHYTCRAENRLGSQQRALDLSV 342
Cdd:cd20969    17 GHTVQFVCRADGDPPPAILWLSPRKHLVSAKSNGRLTVfpdgTLEVRYAQVQDNGTYLCIAANAGGNDSMPAHLHV 92

Immunoglobulin (Ig)-like domain at the C-terminus of semaphorins; The members here are composed of the immunoglobulin (Ig)-like domain in semaphorins. Semaphorins are transmembrane protein that have important roles in a variety of tissues. Functionally, semaphorins were initially characterized for their importance in the development of the nervous system and in axonal guidance. Later they have been found to be important for the formation and functioning of the cardiovascular, endocrine, gastrointestinal, hepatic, immune, musculoskeletal, renal, reproductive, and respiratory systems. Semaphorins function through binding to their receptors and transmembrane semaphorins also serves as receptors themselves. Although molecular mechanism of semaphorins is poorly understood, the Ig-like domains may be involved in ligand binding or dimerization.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1622895094 271 GQFLRLLCaadSQPP--ATLSWVLQDRVLSLSHP----WGPRTlGLELPGVKAGDSGHYTCRAENR-LGSQQRALDLSVQ 343
Cdd:cd04979    11 GDTVILSC---SVKSnnAPVTWIHNGKKVPRYRSprlvLKTER-GLLIRSAQEADAGVYECHSGERvLGSTLRSVTLHVL 86

                  ..
gi 1622895094 344 YP 345
Cdd:cd04979    87 ER 88

Second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor; member of the I-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor. FGF receptors bind FGF signaling polypeptides. FGFs participate in multiple processes such as morphogenesis, development, and angiogenesis. FGFs bind to four FGF receptor tyrosine kinases (FGFR1, FGFR2, FGFR3, FGFR4). Receptor diversity is controlled by alternative splicing producing splice variants with different ligand binding characteristics and different expression patterns. FGFRs have an extracellular region comprised of three IG-like domains, a single transmembrane helix, and an intracellular tyrosine kinase domain. Ligand binding and specificity reside in the Ig-like domains 2 and 3, and the linker region that connects these two. FGFR activation and signaling depend on FGF-induced dimerization, a process involving cell surface heparin or heparin sulfate proteoglycans.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 1622895094 274 LRLLCAADSQPPATLSWVLQDRVLSLSHPWG-----PRTLGLELPGVKAGDSGHYTCRAENRLGSQQRALDLSV 342
Cdd:cd05857    22 VKFRCPAAGNPTPTMRWLKNGKEFKQEHRIGgykvrNQHWSLIMESVVPSDKGNYTCVVENEYGSINHTYHLDV 95

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

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                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1622895094   29 VMVQEGLCVSVSCSFNYPSrgwtestPAYGYWFKagtetetskdapvatnnqNREVEMSTQGRFQLTGDPGkkSCSLVIR 108
Cdd:smart00410   4 VTVKEGESVTLSCEASGSP-------PPEVTWYK------------------QGGKLLAESGRFSVSRSGS--TSTLTIS 56

                           90
                   ....*....|....*
gi 1622895094  109 DAQMWDEARYFFRVE 123
Cdd:smart00410  57 NVTPEDSGTYTCAAT 71