First (N-terminal) immunoglobulin (Ig)-like domain of nectin-like molecule-3; 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-3, Necl-3 (also known as cell adhesion molecule 2 (CADM2), SynCAM2, IGSF4D). 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-3 accumulates in central and peripheral nervous system tissue, and has been shown to selectively interact with oligodendrocytes.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 194381454  35 FPLTQNVTVVEGGTAILTCRVDQNDNTSLQWSNPAQQTLYFDDKKALRDNRIELVRASWHELSISVSDVSLSDEGQYTCS 114
Cdd:cd07701    1 FPLTQNVTVVEGGTANLTCRVDQNDNTSLQWSNPAQQTLYFDDKKALRDNRIELVRASWHELSISISDVSLSDEGQYTCS 80

                         90
                 ....*....|....*.
gi 194381454 115 LFTMPVKTSKAYLTVL 130
Cdd:cd07701   81 LFTMPVKTSKAYLTVL 96

putative band 4.1 homologues' binding motif;

                           10
                   ....*....|....*...
gi 194381454   303 YRYLARHKGTYLTNEAKG 320
Cdd:smart00294   2 YRYKHRDEGSYHTHEPKG 19

First (N-terminal) immunoglobulin (Ig)-like domain of nectin-like molecule-3; 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-3, Necl-3 (also known as cell adhesion molecule 2 (CADM2), SynCAM2, IGSF4D). 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-3 accumulates in central and peripheral nervous system tissue, and has been shown to selectively interact with oligodendrocytes.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 194381454  35 FPLTQNVTVVEGGTAILTCRVDQNDNTSLQWSNPAQQTLYFDDKKALRDNRIELVRASWHELSISVSDVSLSDEGQYTCS 114
Cdd:cd07701    1 FPLTQNVTVVEGGTANLTCRVDQNDNTSLQWSNPAQQTLYFDDKKALRDNRIELVRASWHELSISISDVSLSDEGQYTCS 80

                         90
                 ....*....|....*.
gi 194381454 115 LFTMPVKTSKAYLTVL 130
Cdd:cd07701   81 LFTMPVKTSKAYLTVL 96

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 194381454    39 QNVTVVEGGTAILTCRVDQNDNTSLQWSNPAQQTLYFDDKKALRDNrielvrASWHELSIsvSDVSLSDEGQYTCSL-FT 117
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGSPPPEVTWYKQGGKLLAESGRFSVSRS------GSTSTLTI--SNVTPEDSGTYTCAAtNS 73

                           90
                   ....*....|..
gi 194381454   118 MPVKTSKAYLTV 129
Cdd:smart00410  74 SGSASSGTTLTV 85

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 194381454   39 QNVTVVEGGTAILTCRVDQNDNTSLQWsnpaqqtlYFDDKKaLRDNRIELVRASWHELSISVSDVSLSDEGQYTC 113
Cdd:pfam13927   9 SSVTVREGETVTLTCEATGSPPPTITW--------YKNGEP-ISSGSTRSRSLSGSNSTLTISNVTRSDAGTYTC 74

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

                           10        20        30        40        50        60
                   ....*....|....*....|....*....|....*....|....*....|....*....|..
gi 194381454   248 QEGQPLILTCESKGKPLPEpVLWTKDGGE-LPDPDRMVVSGRELN-ILFLNKT---DNGTYR 304
Cdd:smart00410   7 KEGESVTLSCEASGSPPPE-VTWYKQGGKlLAESGRFSVSRSGSTsTLTISNVtpeDSGTYT 67

First (N-terminal) immunoglobulin (Ig)-like domain of nectin-like molecule-3; 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-3, Necl-3 (also known as cell adhesion molecule 2 (CADM2), SynCAM2, IGSF4D). 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-3 accumulates in central and peripheral nervous system tissue, and has been shown to selectively interact with oligodendrocytes.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 194381454  35 FPLTQNVTVVEGGTAILTCRVDQNDNTSLQWSNPAQQTLYFDDKKALRDNRIELVRASWHELSISVSDVSLSDEGQYTCS 114
Cdd:cd07701    1 FPLTQNVTVVEGGTANLTCRVDQNDNTSLQWSNPAQQTLYFDDKKALRDNRIELVRASWHELSISISDVSLSDEGQYTCS 80

                         90
                 ....*....|....*.
gi 194381454 115 LFTMPVKTSKAYLTVL 130
Cdd:cd07701   81 LFTMPVKTSKAYLTVL 96

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 194381454  36 PLTQNVTVVEGGTAILTCRVDQNDNTSLQWSNPAQQTLYFDDKKALRDNRIELVRASWHELSISVSDVSLSDEGQYTCSL 115
Cdd:cd05717    1 PHTQDVTVVEGETLTLKCQVSLRDDSSLQWLNPNGQTIYFNDKRALRDSRYQLLNHSASELSISVSNVTLSDEGVYTCLH 80

                         90
                 ....*....|....
gi 194381454 116 FTMPVKTSKAYLTV 129
Cdd:cd05717   81 YTDPVSTKKVTVTV 94

Second immunoglobulin (Ig)-like domain of nectin-like molcule-1 (Necl-1); member of the I-set of Ig superfamily domains; The members here are composed of the second immunoglobulin (Ig)-like domain of nectin-like molcule-1 (Necl-1; also known as cell adhesion molecule3 (CADM3)). These nectin-like molecules have similar domain structures to those of nectins. At least five nectin-like molecules have been identified (Necl-1 through Necl-5). These have an extracellular region containing three Ig-like domains, one transmembrane region, and one 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 and Necl-2 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. Ig domains are likely to participate in ligand binding and recognition.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 194381454 130 LGVPEKPQISGFSSPVMEGDLMQLTCKTSGSKPAADIRWFKNDKEIKDVKYLKEEDANRKTFTVSSTLDFRVDRSDDGVA 209
Cdd:cd07705    1 LGIPQKPQITGYESAFKEKDKAKLRCTSSGSKPAANIKWRKGDQELEGAPTSVQEDGNGKTFTVSSSVEFQVTREDDGAE 80

                         90       100
                 ....*....|....*....|...
gi 194381454 210 VICRVDHESLNATPQVAMQVLEI 232
Cdd:cd07705   81 ITCSVGHESLHDSDRSTSQRIEV 103

Second immunoglobulin (Ig)-like domain of nectin-like molecule-4 (Necl-4); member of the I-set of Ig superfamily domains; The members here are composed of the second immunoglobulin (Ig)-like domain of nectin-like molecule-4 (Necl-4; also known as cell adhesion molecule 4 (CADM4)). Nectin-like molecules have similar domain structures to those of nectins. At least five nectin-like molecules have been identified (Necl-1-Necl-5). These have an extracellular region containing three Ig-like domains, one transmembrane region, and one cytoplasmic region. Ig domains are likely to participate in ligand binding and recognition. Necl-4 is expressed on Schwann cells, and plays a key part in initiating peripheral nervous system (PNS) myelination. In injured peripheral nerve cells, the mRNA signal for both Necl-4 and Necl-5 was observed to be elevated. Necl-4 participates in cell-cell adhesion and is proposed to play a role in tumor suppression.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 194381454 133 PEKPQISgFSSPVMEGDLMQLTCKTSGSKPAADIRWFKNDKEIKDVKYLKEedaNRKTFTVSSTLDFRVDRSDDGVAVIC 212
Cdd:cd05885    4 PENPVVE-VREQAVEGGEVELSCLVPRSRPAATLRWYRDRKELKGVSSGQE---NGKVWSVASTVRFRVDRKDDGGIVIC 79

                 ....*..
gi 194381454 213 RVDHESL 219
Cdd:cd05885   80 EAQNQAL 86

CD80-like C2-set immunoglobulin domain; These domains belong to the immunoglobulin superfamily.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 194381454  153 LTCKTSGSKPAADIRWFKNDKEIKDVKYLKEEDANRKTFTVSSTLDFRVDRSDDGVAVICRVDHESL 219
Cdd:pfam08205  19 ATCSSAGGKPAPRITWYLDGKPLEAAETSSEQDPESGLVTVTSELKLVPSRSDHGQSLTCQVSYGAL 85

Second immunoglobulin (Ig)-like domain of Kirrel (kin of irregular chiasm-like) 3, and similar domains; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the second immunoglobulin (Ig)-like domain of Kirrel (kin of irregular chiasm-like) 3 (also known as Neph2). This protein has five Ig-like domains, one transmembrane domain, and a cytoplasmic tail. Included in this group is mammalian Kirrel (Neph1), Kirrel2 (Neph3), and Drosophila RST (irregular chiasm C-roughest) protein. These proteins contain multiple Ig domains, have properties of cell adhesion molecules, and are important in organ development.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 194381454 136 PQISGfsSPVME---GDLMQLTCKTSGSKPAADIRWFKNDKEIKDVKYLKEEDANRKTFTVSSTLDFRVDRSDDGVAVIC 212
Cdd:cd05759    2 PVIEG--GPVISlqaGVPYNLTCRARGAKPAAEIIWFRDGEQLEGAVYSKELLKDGKRETTVSTLLITPSDLDTGRTFTC 79

                 ....*..
gi 194381454 213 RVDHESL 219
Cdd:cd05759   80 RARNEAI 86

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|...
gi 194381454  236 PSVKIIPSTPFPQEGQPLILTCESKGKPLPEpVLWTKDGGELPD----PDRMVVSGRELNILFLNKTDNGTYR 304
Cdd:pfam13927   2 PVITVSPSSVTVREGETVTLTCEATGSPPPT-ITWYKNGEPISSgstrSRSLSGSNSTLTISNVTRSDAGTYT 73

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 194381454   41 VTVVEGGTAILTCRV---DQNDNTSLQWS------NPAQQTLYF--DDKKALRDNRIELVRA-SWHELSISVSDVSLSDE 108
Cdd:pfam07686   6 VTVALGGSVTLPCTYsssMSEASTSVYWYrqppgkGPTFLIAYYsnGSEEGVKKGRFSGRGDpSNGDGSLTIQNLTLSDS 85

                          90       100
                  ....*....|....*....|....
gi 194381454  109 GQYTCSLFTMP--VKTSKAYLTVL 130
Cdd:pfam07686  86 GTYTCAVIPSGegVFGKGTRLTVL 109

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 194381454  135 KPQISGFSSP--VMEGDLMQLTCKTSGSkPAADIRWFKNDKEIKDVKYLK-EEDANRKTFTVSStldfrVDRSDDGV 208
Cdd:pfam13927   1 KPVITVSPSSvtVREGETVTLTCEATGS-PPPTITWYKNGEPISSGSTRSrSLSGSNSTLTISN-----VTRSDAGT 71

Second immunoglobulin (Ig) domain of Nectin-2 and Nectin-like protein 5, and similar domains; member of the C1-set of the Ig superfamily (IgSF) domains; The members here are composed of the second immunoglobulin (Ig) domain of nectin-2 (also known as poliovirus receptor related protein 2 or Cluster of Differentiation 112 (CD112)), nectin-like protein 5 (CD155), and similar proteins. Nectins and Nectin-like molecules are a family of Ca(2+)-independent immunoglobulin-like transmembrane glycoproteins belonging to the class of adhesion receptors, consisting of nine members (nectins 1 through 4 and nectin-like proteins 1 through 5). Nectins are synaptic cell adhesion molecules (CAMs) which facilitate adhesion and signaling at various intracellular junctions. Nectins form homophilic cis-dimers, followed by homophilic and heterophilic trans-dimers involved in cell-cell adhesion. Nectin-2 and nectin-3 localize at Sertoli-spermatid junctions where they form heterophilic trans-interactions between the cells that are essential for the formation and maintenance of the junctions and for spermatid development. CD155 is the fifth member in the nectin-like molecule family, and functions as the receptor of poliovirus; therefore, CD155 is also referred to as Necl-5, or PVR. In contrast to all other family members, CD155 lacks self-adhesion capacity, yet it shares with nectins the feature to interact with other nectins. For instance, CD155 heterophilically trans-interacts with nectin-3, thereby contributing significantly to the establishment of adherens junctions between epithelial cells. This group belongs to the Constant 1 (C1)-set of IgSF domains, which has one beta-sheet that is formed by strands A-B-E-D and the other strands by G-F-C-C'.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 194381454 136 PQISGFSSPVMEGDLMQL--TCKTSGSKPAADIRWFKNDKeiKDVKYLKEEDANRKTFTVSSTLDFRVDRSDDGVAVICR 213
Cdd:cd07703    1 PKNSAEAQEVQAGGIPVPvaRCVSANGRPPARISWSSTLN--GNANTTQVPGPDSGTVTVTSEYSLVPTPEANGKEVTCK 78

                 ....*..
gi 194381454 214 VDHESLN 220
Cdd:cd07703   79 VEHETLE 85

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 194381454  147 EGDLMQLTCKTSGSKPAADIRWFKNDKEIKDVkyLKEEDANRKTFTvsSTLDFRVDRSDDGVAVICRVDHESLNATPQVA 226
Cdd:pfam00047  10 EGDSATLTCSASTGSPGPDVTWSKEGGTLIES--LKVKHDNGRTTQ--SSLLISNVTKEDAGTYTCVVNNPGGSATLSTS 85

                  .
gi 194381454  227 M 227
Cdd:pfam00047  86 L 86

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
                 ....*....|....*....|....*....|....*....|....*....|....*....|...
gi 194381454 250 GQPLILTCESKGKPLPEpVLWTKDGGELPdPDRMVVS--GRELNILFLNKTDNGTYRYLARHK 310
Cdd:cd05731   10 GGVLLLECIAEGLPTPD-IRWIKLGGELP-KGRTKFEnfNKTLKIENVSEADSGEYQCTASNT 70

Signal-regulatory protein (SIRP) immunoglobulin-like domain 2; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the immunoglobulin (Ig)-like domain in Signal-Regulatory Protein (SIRP), domain 2 (C1 repeat 1). The SIRPs belong to the "paired receptors" class of membrane proteins that comprise several genes coding for proteins with similar extracellular regions, but very different transmembrane/cytoplasmic regions with different (activating or inhibitory) signaling potentials. They are commonly on NK cells, but are also on many myeloid cells. Their extracellular region contains three Immunoglobulin superfamily domains, a single V-set and two C1-set IgSF domains. Their cytoplasmic tails contain either ITIMs or transmembrane regions that have positively charged residues that allow an association with adaptor proteins, such as DAP12/KARAP, containing ITAMs. There are 3 distinct SIRP members: alpha, beta, and gamma. SIRP alpha (also known as CD172a or SRC homology 2 domain-containing protein tyrosine phosphatase substrate 1/Shps-1) is a membrane receptor that interacts with a ligand CD47 expressed on many cells and gives an inhibitory signal through immunoreceptor tyrosine-based inhibition motifs in the cytoplasmic region that interact with phosphatases SHP-1 and SHP-2. SIRP beta has a short cytoplasmic region and associates with a transmembrane adapter protein DAP12 containing immunoreceptor tyrosine-based activation motifs to give an activating signal. SIRP gamma contains a very short cytoplasmic region lacking obvious signaling motifs, but also binds CD47, but with much less affinity.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 194381454 133 PEKPQISGFSSPVMEGDLMQLTCKTSGSKPAaDI--RWFKNDKEIKDVKYLKEEDANRKTFTVSSTLDFRVDRSDDGVAV 210
Cdd:cd05772    2 PSQPLVSGPSGRATPGQTVSFTCKSHGFSPR-DItlKWFKNGNELSALQTTVFPEGDSVSYSVSSTVQVVLTKDDVHSQL 80

                         90
                 ....*....|..
gi 194381454 211 ICRVDHESLNAT 222
Cdd:cd05772   81 TCEVAHVTLQAP 92

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
                 ....*....|....*....|....*....|....*....|....*....|....*.
gi 194381454 253 LILTCESKGKPLPEpVLWTKDGGELP----DPDRMVVSGRELNILFLNKTDNGTYR 304
Cdd:cd00096    1 VTLTCSASGNPPPT-ITWYKNGKPLPpssrDSRRSELGNGTLTISNVTLEDSGTYT 55

immunoglobulin-like domain of telokin and similar proteins; a member of the I-set of IgSF domains; The members here are composed of the immunoglobulin (Ig) domain in telokin, the C-terminal domain of myosin light chain kinase which is identical to telokin, and similar proteins. 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 telokin Ig domain 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 194381454  40 NVTVVEGGTAILTCRVDQNDNTSLQWSNpaqqtlyfDDKKALRDNRIELVRASWHELSISVSDVSLSDEGQYTC 113
Cdd:cd20973    6 DKEVVEGSAARFDCKVEGYPDPEVKWMK--------DDNPIVESRRFQIDQDEDGLCSLIISDVCGDDSGKYTC 71

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
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|..
gi 194381454 249 EGQPLILTCESKGKPLPEpVLWTKDGGELPdPDRMVV--SGRELNILFLNKTDNGTYRYLARH-----KGTY 313
Cdd:cd05876    9 RGQSLVLECIAEGLPTPT-VKWLRPSGPLP-PDRVKYqnHNKTLQLLNVGESDDGEYVCLAENslgsaRHAY 78

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 194381454 152 QLTCKTSGSkPAADIRWFKNDKEIKDvkylkEEDANRKTFTVSSTLDFR-VDRSDDGVaVICRV 214
Cdd:cd00096    2 TLTCSASGN-PPPTITWYKNGKPLPP-----SSRDSRRSELGNGTLTISnVTLEDSGT-YTCVA 58

Fourth immunoglobulin (Ig)-like domain in neogenin, and similar domains; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain in neogenin and related proteins. Neogenin is a cell surface protein which is expressed in the developing nervous system of vertebrate embryos in the growing nerve cells. It is also expressed in other embryonic tissues, and may play a general role in developmental processes such as cell migration, cell-cell recognition, and tissue growth regulation. Included in this group is the tumor suppressor protein DCC which is deleted in colorectal carcinoma. DCC and neogenin each have four Ig-like domains followed by six fibronectin type III domains, a transmembrane domain, and an intracellular domain. 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 194381454 242 PSTPFPQEGQPLILTCESKGKPLPEpVLWTKDGGE-LPDPDRMVVSGRELNILFLNKTDNGTYRYLA 307
Cdd:cd05723    4 PSNIYAHESMDIVFECEVTGKPTPT-VKWVKNGDVvIPSDYFKIVKEHNLQVLGLVKSDEGFYQCIA 69

Immunoglobulin (Ig)-like domain of vascular endothelial growth factor (VEGF) receptor (R) and similar proteins; member of the I-set of IgSF domains; The members here are composed of the immunoglobulin (Ig)-like domain of vascular endothelial growth factor (VEGF) receptor (R) and related proteins. The VEGFRs have an extracellular component with seven Ig-like domains, a transmembrane segment, and an intracellular tyrosine kinase domain interrupted by a kinase-insert domain. The VEGFR family consists of three members: VEGFR-1 (Flt-1), VEGFR-2 (KDR/Flk-1) and VEGFR-3 (Flt-4). VEGF-A interacts with both VEGFR-1 and VEGFR-2. VEGFR-1 binds strongest to VEGF; VEGF-2 binds more weakly. VEGFR-3 appears not to bind VEGF, but binds other members of the VEGF family (VEGF-C and -D). VEGFRs bind VEGFs with high affinity with the IG-like domains. VEGF-A is important to the growth and maintenance of vascular endothelial cells and to the development of new blood- and lymphatic-vessels in physiological and pathological states. VEGFR-2 is a major mediator of the mitogenic, angiogenic, and microvascular permeability-enhancing effects of VEGF-A. VEGFR-1 may play an inhibitory part in these processes by binding VEGF and interfering with its interaction with VEGFR-2. VEGFR-1 has a signaling role in mediating monocyte chemotaxis. VEGFR-1 and VEGFR-2 may mediate a chemotactic and a survival signal in hematopoietic stem cells or leukemia cells. VEGFR-3 has been shown to be involved in tumor angiogenesis and growth. This group also contains alpha-type platelet-derived growth factor receptor precursor (PDGFR)-alpha (CD140a), and PDGFR-beta (CD140b). PDGFRs alpha and beta have an extracellular component with five Ig-like domains, a transmembrane segment, and a cytoplasmic portion that has protein tyrosine kinase activity.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 194381454  35 FPLTQNVTVVEGGTAILTCRVDQNDNT--SLQWSNPAQQTlyfDDKKALRDNRIELVRASWHELSI-SVSDVSLSDEGQY 111
Cdd:cd05742    6 SPNAEPTVLPQGETLVLNCTANVNLNEvvDFQWTYPSEKE---GKLALLKPDIKVDWSEPGEFVSTlTIPEATLKDSGTY 82

                         90
                 ....*....|....
gi 194381454 112 TCSLFTMPVKTSKA 125
Cdd:cd05742   83 TCAARSGVMKKEKQ 96

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

                           10        20        30        40        50        60
                   ....*....|....*....|....*....|....*....|....*....|....*....|..
gi 194381454   248 QEGQPLILTCESKGKPLPEpVLWTKDGGE-LPDPDRMVVSGRELN-ILFLNKT---DNGTYR 304
Cdd:smart00410   7 KEGESVTLSCEASGSPPPE-VTWYKQGGKlLAESGRFSVSRSGSTsTLTISNVtpeDSGTYT 67

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
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 194381454 236 PSVKIIPSTPFpQEGQPLILTCESKGkpLPEPVLWTKDGGELPDPDRMVVSG--RELNILFLNKTDNGTYR 304
Cdd:cd05740    2 PFISSNNSNPV-EDKDAVTLTCEPET--QNTSYLWWFNGQSLPVTPRLTLSNgnRTLTLLNVTREDAGAYQ 69

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 194381454 248 QEGQPLILTCESKGKPLPEpVLWTKDGGELPDPDRM-----------VVSgrELNILFLNKTDNGTYRYLARHKGTYLTN 316
Cdd:cd20956   14 QPGPSVSLKCVASGNPLPQ-ITWTLDGFPIPESPRFrvgdyvtsdgdVVS--YVNISSVRVEDGGEYTCTATNDVGSVSH 90

                 ...
gi 194381454 317 EAK 319
Cdd:cd20956   91 SAR 93

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        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 194381454 237 SVKIIPSTPFPQEGQPLILTCESKGKPLPEpVLWTKDGGELPDPDRMVVSGRE-LNILFLNKTDNGTYRYLARhkgtylt 315
Cdd:cd20957    3 SATIDPPVQTVDFGRTAVFNCSVTGNPIHT-VLWMKDGKPLGHSSRVQILSEDvLVIPSVKREDKGMYQCFVR------- 74

                 ....*..
gi 194381454 316 NEAKGAE 322
Cdd:cd20957   75 NDGDSAQ 81

Immunoglobulin variable domain (IgV); The members here are composed of the immunoglobulin variable domain (IgV). The IgV family contains the standard Ig superfamily V-set AGFCC'C"/DEB domain topology, and are components of immunoglobulin (Ig) and T cell receptors. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. In Ig, each chain is composed of one variable domain (IgV) and one or more constant domains (IgC); these names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. Within the variable domain, there are regions of even more variability called the hypervariable or complementarity-determining regions (CDRs) which are responsible for antigen binding. A predominant feature of most Ig domains is the disulfide bridge connecting 2 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" strands in the other.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 194381454  37 LTQN---VTVVEGGTAILTCRVDQ-NDNTSLQW--SNPAQQ---TLYFDDKKALRD----NRIELVRASWHELSISVSDV 103
Cdd:cd00099    1 VTQSprsLSVQEGESVTLSCEVSSsFSSTYIYWyrQKPGQGpefLIYLSSSKGKTKggvpGRFSGSRDGTSSFSLTISNL 80

                         90
                 ....*....|...
gi 194381454 104 SLSDEGQYTCSLF 116
Cdd:cd00099   81 QPEDSGTYYCAVS 93

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 194381454  49 AILTCRVDQNDNTSLQWsnpaqqtlyFDDKKALRDNRIELVRASWHELSISVSDVSLSDEGQYTC 113
Cdd:cd00096    1 VTLTCSASGNPPPTITW---------YKNGKPLPPSSRDSRRSELGNGTLTISNVTLEDSGTYTC 56

Second immunoglobulin (Ig) domain of poliovirus receptor (PVR, also known as CD155 and Necl-5), and similar domains; member of the C1-set of Ig superfamily (IgSF) domains; The members here are composed of the second immunoglobulin (Ig) domain of poliovirus receptor (PVR, also known as CD155 and nectin-like protein 5 (Necl-5)) and similar proteins. Poliovirus (PV) binds to its cellular receptor (PVR/CD155) to initiate infection. CD155 is a membrane-anchored, single-span glycoprotein; its extracellular region has three Ig-like domains. There are four different isotypes of CD155 (referred to as alpha, beta, gamma, and delta), these result from alternate splicing of the CD155 mRNA, and have identical extracellular domains. CD155-beta and CD155-gamma are secreted, while CD155-alpha and CD155-delta are membrane-bound and function as PV receptors. The virus recognition site is contained in the amino-terminal domain, D1. Having the virus attachment site on the receptor distal from the plasma membrane may be important for successful initiation of infection of cells by the virus. CD155 binds in the poliovirus "canyon" and has a footprint similar to that of the intercellular adhesion molecule-1 receptor on human rhinoviruses. This group also includes the second Ig-like domain of nectin-1, also known as poliovirus receptor related protein(PVRL)1 or CD111.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 194381454 154 TCKTSGSKPAADIRWfknDKEIKDVKYLKEEDANRKTFTVSSTLDFRVDRSDDGVAVICRVDHESL 219
Cdd:cd05719   22 TCISANGKPPASVTW---ETDLKGEASTTQVRGSNGTVTVTSRYRLVPSREADGQPLTCVVEHPSL 84

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.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 194381454 145 VMEGDLMQLTCKTSGSkPAADIRWFKNDKEIKDVKY--LKEEDANRKTFTVSstldfRVDRSDDG 207
Cdd:cd05737   13 IMEGKTLNLTCNVWGD-PPPEVSWLKNDQALAFLDHcnLKVEAGRTVYFTIN-----GVSSEDSG 71

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
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 194381454  39 QNVTVVEGGTAILTCRVDQNDNTSLQWSNPAQqtlyfddkkALRDNRIELVRASWHELSISVSDVSLSDEGQYT 112
Cdd:cd05747   11 RSLTVSEGESARFSCDVDGEPAPTVTWMREGQ---------IIVSSQRHQITSTEYKSTFEISKVQMSDEGNYT 75

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 194381454  39 QNVTVVEGGTAILTCRVDqndntslqwSNPAQQTLYFDDKKALRDNRIELvrasWHELSISVSDVSLSDEGQYTCSLFTM 118
Cdd:cd05725    5 QNQVVLVDDSAEFQCEVG---------GDPVPTVRWRKEDGELPKGRYEI----LDDHSLKIRKVTAGDMGSYTCVAENM 71

                         90
                 ....*....|..
gi 194381454 119 PVKTS-KAYLTV 129
Cdd:cd05725   72 VGKIEaSATLTV 83

First immunoglobulin variable (IgV) domain of nectin-3 (also known as poliovirus receptor related protein 3), and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of nectin-3 (also known as poliovirus receptor related protein 3 (PVRL3) or cluster of differentiation (CD) 113). Nectin-3 belongs to the nectin family comprised of four transmembrane glycoproteins (nectins-1 through -4). Nectins are synaptic cell adhesion molecules (CAMs) which participate in adhesion and signaling at various intracellular junctions. Nectins form homophilic cis-dimers, followed by homophilic and heterophilic trans-dimers involved in cell-cell adhesion. For example, during spermatid development, the nectin-3,-2 trans-interaction is required for the formation of Sertoli cell-spermatid junctions in testis, and during morphogenesis of the ciliary body, the nectin-3,-1 trans-interaction is important for apex-apex adhesion between the pigment and non-pigment layers of the ciliary epithelia. Nectins also heterophilically trans-interact with other CAMs such as nectin-like molecules (Necls); nectin-3 for example, trans-interacts with Necl-5, regulating cell movement and proliferation. Other proteins with which nectin-3 interacts include the actin filament-binding protein, afadin, integrin alpha-beta3, Par-3, and PDGF receptor; its interaction with PDGF receptor regulates the latter's signaling for anti-apoptosis.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 194381454  41 VTVVEGGTAILTCRVDQNDN-TSLQWSN---PAQQTL------YFDDKKALRDNRIELVRASWHELSISVSDVSLSDEGQ 110
Cdd:cd05887    9 VTAVWGKNVSLKCLIEVNETiTQISWEKihgKSSQTVavhhpqYGISIQGEYQGRVSFKNYSLNDATITLHNVGFSDSGK 88

                         90
                 ....*....|....*....
gi 194381454 111 YTCSLFTMPVKTSKAYLTV 129
Cdd:cd05887   89 YICKAVTFPLGNAQSSTTV 107