First (N-terminal) immunoglobulin (Ig)-like domain of nectin-like molecule 2; 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-2, Necl-2 (also known as cell adhesion molecule 1 (CADM1), SynCAM1, IGSF4A, Tslc1, sgIGSF, and RA175). 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-2 has Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-2 is expressed in a wide variety of tissues and is a putative tumour suppressor gene, which is downregulated in aggressive neuroblastoma.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 568959839  50 LFTKDVTVIEGEVATISCQVNKSDDSVIQLLNPNRQTIYFRDFRPLKDSRFQLLNFSSSELKVSLTNVSISDEGRYFCQL 129
Cdd:cd05881    1 LVTEDVTVVEGEVATISCRVKNSDDSVIQLLNPNRQTIYFRDFRPLKDSRFQLVNFSSSELRVSLTNVSISDEGRYFCQL 80

                         90
                 ....*....|....
gi 568959839 130 YTDPPQESYTTITV 143
Cdd:cd05881   81 YTDPPQEAYTTITV 94

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 568959839   255 PLQGLTREGDAFELTCEAIGKPQPvMVTWVRVDDEM---PQHAVLSGPN----LFINNLNKTDNGTYRCEASNIVGKAHS 327
Cdd:smart00410   1 PPSVTVKEGESVTLSCEASGSPPP-EVTWYKQGGKLlaeSGRFSVSRSGststLTISNVTPEDSGTYTCAATNSSGSASS 79

                   ....*.
gi 568959839   328 DYMLYV 333
Cdd:smart00410  80 GTTLTV 85

First (N-terminal) immunoglobulin (Ig)-like domain of nectin-like molecule 2; 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-2, Necl-2 (also known as cell adhesion molecule 1 (CADM1), SynCAM1, IGSF4A, Tslc1, sgIGSF, and RA175). 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-2 has Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-2 is expressed in a wide variety of tissues and is a putative tumour suppressor gene, which is downregulated in aggressive neuroblastoma.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 568959839  50 LFTKDVTVIEGEVATISCQVNKSDDSVIQLLNPNRQTIYFRDFRPLKDSRFQLLNFSSSELKVSLTNVSISDEGRYFCQL 129
Cdd:cd05881    1 LVTEDVTVVEGEVATISCRVKNSDDSVIQLLNPNRQTIYFRDFRPLKDSRFQLVNFSSSELRVSLTNVSISDEGRYFCQL 80

                         90
                 ....*....|....
gi 568959839 130 YTDPPQESYTTITV 143
Cdd:cd05881   81 YTDPPQEAYTTITV 94

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 568959839   255 PLQGLTREGDAFELTCEAIGKPQPvMVTWVRVDDEM---PQHAVLSGPN----LFINNLNKTDNGTYRCEASNIVGKAHS 327
Cdd:smart00410   1 PPSVTVKEGESVTLSCEASGSPPP-EVTWYKQGGKLlaeSGRFSVSRSGststLTISNVTPEDSGTYTCAATNSSGSASS 79

                   ....*.
gi 568959839   328 DYMLYV 333
Cdd:smart00410  80 GTTLTV 85

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 568959839  245 KPQVHIQmtyPLQGLTREGDAFELTCEAIGKPQPVmVTWVRVDDEM------PQHAVLSGPNLFINNLNKTDNGTYRCEA 318
Cdd:pfam13927   1 KPVITVS---PSSVTVREGETVTLTCEATGSPPPT-ITWYKNGEPIssgstrSRSLSGSNSTLTISNVTRSDAGTYTCVA 76

                  ..
gi 568959839  319 SN 320
Cdd:pfam13927  77 SN 78

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 568959839    53 KDVTVIEGEVATISCQVNKSDDSVIQLLNPNRQTIYFRDfrplkdsRFQLlnfSSSELKVSLT--NVSISDEGRYFCQLY 130
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGSPPPEVTWYKQGGKLLAESG-------RFSV---SRSGSTSTLTisNVTPEDSGTYTCAAT 71

                           90
                   ....*....|....
gi 568959839   131 TDPPQ-ESYTTITV 143
Cdd:smart00410  72 NSSGSaSSGTTLTV 85

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

                           10        20        30        40        50        60
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 568959839   158 TAVEGEEIEVNCTAmASKPATTIRWFKGNKELKGKSEVEEWSDMYTVTSQLMLKVHKEDDGVpVICQVE 226
Cdd:smart00410   5 TVKEGESVTLSCEA-SGSPPPEVTWYKQGGKLLAESGRFSVSRSGSTSTLTISNVTPEDSGT-YTCAAT 71

First (N-terminal) immunoglobulin (Ig)-like domain of nectin-like molecule 2; 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-2, Necl-2 (also known as cell adhesion molecule 1 (CADM1), SynCAM1, IGSF4A, Tslc1, sgIGSF, and RA175). 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-2 has Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-2 is expressed in a wide variety of tissues and is a putative tumour suppressor gene, which is downregulated in aggressive neuroblastoma.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 568959839  50 LFTKDVTVIEGEVATISCQVNKSDDSVIQLLNPNRQTIYFRDFRPLKDSRFQLLNFSSSELKVSLTNVSISDEGRYFCQL 129
Cdd:cd05881    1 LVTEDVTVVEGEVATISCRVKNSDDSVIQLLNPNRQTIYFRDFRPLKDSRFQLVNFSSSELRVSLTNVSISDEGRYFCQL 80

                         90
                 ....*....|....
gi 568959839 130 YTDPPQESYTTITV 143
Cdd:cd05881   81 YTDPPQEAYTTITV 94

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 568959839  50 LFTKDVTVIEGEVATISCQVNKSDDSVIQLLNPNRQTIYFRDFRPLKDSRFQLLNFSSSELKVSLTNVSISDEGRYFCQL 129
Cdd:cd05717    1 PHTQDVTVVEGETLTLKCQVSLRDDSSLQWLNPNGQTIYFNDKRALRDSRYQLLNHSASELSISVSNVTLSDEGVYTCLH 80

                         90
                 ....*....|....
gi 568959839 130 YTDPPQESYTTITV 143
Cdd:cd05717   81 YTDPVSTKKVTVTV 94

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 568959839  51 FTKDVTVIEGEVATISCQVNKSDDSVIQLLNPNRQTIYFRDFRPLKDSRFQLLNFSSSELKVSLTNVSISDEGRYFCQLY 130
Cdd:cd07701    3 LTQNVTVVEGGTANLTCRVDQNDNTSLQWSNPAQQTLYFDDKKALRDNRIELVRASWHELSISISDVSLSDEGQYTCSLF 82

                         90
                 ....*....|....
gi 568959839 131 TDPPQESYTTITVL 144
Cdd:cd07701   83 TMPVKTSKAYLTVL 96

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 568959839 144 LVPPRNLMIDIqKDTAVEGEEIEVNCTAMASKPATTIRWFKGNKELKGKSEVEEWSDMYTVTSQLMLKVHKEDDGVPVIC 223
Cdd:cd05885    1 LVAPENPVVEV-REQAVEGGEVELSCLVPRSRPAATLRWYRDRKELKGVSSGQENGKVWSVASTVRFRVDRKDDGGIVIC 79

                         90
                 ....*....|....*....
gi 568959839 224 QVEHPAVTGNLQTQRYLEV 242
Cdd:cd05885   80 EAQNQALPSGHSKQTQYVL 98

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 568959839 155 QKDTAvegeeiEVNCTAMASKPATTIRWFKGNKELKG-KSEVEEWSD--MYTVTSQLMLKVHKEDDGVPVICQVEHPAVT 231
Cdd:cd07705   18 EKDKA------KLRCTSSGSKPAANIKWRKGDQELEGaPTSVQEDGNgkTFTVSSSVEFQVTREDDGAEITCSVGHESLH 91

                 .
gi 568959839 232 G 232
Cdd:cd07705   92 D 92

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

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|...
gi 568959839  160 VEGEEIEVNCTAMASKPATTIRWFKGNKELKG---KSEVEEWSDMYTVTSQLMLKVHKEDDGVPVICQVEHPA 229
Cdd:pfam08205  12 GEGPEVVATCSSAGGKPAPRITWYLDGKPLEAaetSSEQDPESGLVTVTSELKLVPSRSDHGQSLTCQVSYGA 84

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 568959839 266 FELTCEAIGKPQPVmVTWVRVDDEMPQHAVLSGPN------LFINNLNKTDNGTYRCEASNIVGKAHS 327
Cdd:cd00096    1 VTLTCSASGNPPPT-ITWYKNGKPLPPSSRDSRRSelgngtLTISNVTLEDSGTYTCVASNSAGGSAS 67

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 568959839    53 KDVTVIEGEVATISCQVNKSDDSVIQLLNPNRQTIYFRDfrplkdsRFQLlnfSSSELKVSLT--NVSISDEGRYFCQLY 130
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGSPPPEVTWYKQGGKLLAESG-------RFSV---SRSGSTSTLTisNVTPEDSGTYTCAAT 71

                           90
                   ....*....|....
gi 568959839   131 TDPPQ-ESYTTITV 143
Cdd:smart00410  72 NSSGSaSSGTTLTV 85

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

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 568959839 263 GDAFELTCEAIGKPQPvMVTWVRVDDEMPQHAVL--SGPNLFINNLNKTDNGTYRCEASNIVGKAHSDYMLYVY 334
Cdd:cd04968   16 GQTVTLECFALGNPVP-QIKWRKVDGSPSSQWEIttSEPVLEIPNVQFEDEGTYECEAENSRGKDTVQGRIIVQ 88

Immunoglobulin domain; This domain contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 568959839  260 TREGDAFELTCEAIGKPQPVmVTWVRVDDEMPQHavlsgPNLFINNLNKTDNGTYRCEASNIVGKAHSDYM 330
Cdd:pfam13895  11 VTEGEPVTLTCSAPGNPPPS-YTWYKDGSAISSS-----PNFFTLSVSAEDSGTYTCVARNGRGGKVSNPV 75

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
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 568959839 262 EGDAFELTCEAIGKPQPVmVTWVRVDDEMP---QHAVLSGPNLFINNLNKTDNGTYRCEASNIVG 323
Cdd:cd05745    1 EGQTVDFLCEAQGYPQPV-IAWTKGGSQLSvdrRHLVLSSGTLRISRVALHDQGQYECQAVNIVG 64

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

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|..
gi 568959839 263 GDAFELTCEA-IGKPQPVmVTWVR----VDDEMPQHAVLSGPNLFINNLNKTDNGTYRCEASNIVGKAHSDY 329
Cdd:cd05724   12 GEMAVLECSPpRGHPEPT-VSWRKdgqpLNLDNERVRIVDDGNLLIAEARKSDEGTYKCVATNMVGERESRA 82

Second immunoglobulin (Ig)-like domain of Axl/Tyro3 family receptor tyrosine kinases (RTKs); member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the second immunoglobulin (Ig)-like domain in the Axl/Tyro3 family of receptor tyrosine kinases (RTKs). This family includes Axl (also known as Ark, Ufo, and Tyro7), Tyro3 (also known as Sky, Rse, Brt, Dtk, and Tif), and Mer (also known as Nyk, c-Eyk, and Tyro12). Axl/Tyro3 family receptors have an extracellular portion with two Ig-like domains followed by two fibronectin-types III (FNIII) domains, a membrane-spanning single helix, and a cytoplasmic tyrosine kinase domain. Axl, Tyro3, and Mer are widely expressed in adult tissues, though they show higher expression in the brain, lymphatic and vascular systems, and testis. Axl, Tyro3, and Mer bind the vitamin K dependent protein Gas6 with high affinity, and in doing so activate their tyrosine kinase activity. Axl/Gas6 signaling may play a part in cell adhesion processes, prevention of apoptosis, and cell proliferation.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 568959839 263 GDAFELTCEAIGKPQPVMVTWVRVDDEMPQHAVLSGPNLFINNLNKTdnGTYRCEASNIVGKAHS 327
Cdd:cd05749   14 NTPFNLTCQAVGPPEPVEILWWQGGSPLGGPPAPSPSVLNVPGLNET--TKFSCEAHNAKGLTSS 76

Third immunoglobulin domain of Nectin-like Protein-5, and similar domains; The members here are composed of the third immunoglobulin domain of Nectin-like Protein-5 (also known as Cluster of Differentiation 155 (CD155)). Nectin-like Protein-5 mediates NK (Natural Killer) cell adhesion and triggers NK cell effector functions. CD155 binds two different NK cell receptors: CD96 and CD226. These interactions accumulate at the cell-cell contact site, leading to the formation of a mature immunological synapse between NK cell and target cell. This may trigger adhesion and secretion of lytic granules and IFN-gamma and activate cytotoxicity of activated NK cells. CD155 may also promote NK cell-target cell modular exchange, and PVR transfer to the NK cell. This transfer is more important in some tumor cells expressing a lot of PVR, and may trigger fratricide NK cell activation, providing tumors with a mechanism of immunoevasion. Moreover, CD155 plays a role in mediating tumor cell invasion and migration.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 568959839 268 LTCEAIGKPQPVMVTWVRVDDEMPQHAVLSGPNLFINNLNKTDNGTYRCEASNIVGKAHSDYMLYV 333
Cdd:cd20930   21 LTCDVRSNPEPTGYDWSTTSGPFPTSAVAQGPQLLIHSVDRLVNTTFICTVTNAVGTGRAEQTIFV 86

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 568959839 261 REGDAFELTCEAIGkpQPVMVTWVRVDDEMPQHA--VLSGPN--LFINNLNKTDNGTYRCEASNIVGKAHSD-YMLYVY 334
Cdd:cd05740   13 EDKDAVTLTCEPET--QNTSYLWWFNGQSLPVTPrlTLSNGNrtLTLLNVTREDAGAYQCEISNPVSANRSDpVTLDVI 89

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 568959839   53 KDVTVIEGEVATISCQVNKSDDSVIQLLNPNRQT---------IYFRDFRP--LKDSRFQLL-NFSSSELKVSLTNVSIS 120
Cdd:pfam07686   4 REVTVALGGSVTLPCTYSSSMSEASTSVYWYRQPpgkgptfliAYYSNGSEegVKKGRFSGRgDPSNGDGSLTIQNLTLS 83

                          90       100
                  ....*....|....*....|....*.
gi 568959839  121 DEGRYFCQLYTDPPQ--ESYTTITVL 144
Cdd:pfam07686  84 DSGTYTCAVIPSGEGvfGKGTRLTVL 109

Fifth immunoglobulin (Ig) domain of contactin; The members here are composed of the fifth 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.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 568959839 256 LQGLTREGDAFeLTCEAIGKPQPVmVTWVRVDD---EMPQHAVLSGPNLFINNLNKTDNGTYRCEASNIVGKAHSDYMLY 332
Cdd:cd04969   11 KILAAKGGDVI-IECKPKASPKPT-ISWSKGTElltNSSRICILPDGSLKIKNVTKSDEGKYTCFAVNFFGKANSTGSLS 88

                 .
gi 568959839 333 V 333
Cdd:cd04969   89 V 89

Immunoglobulin-like Ig0 domain of basigin-1 (BSG1) and similar proteins; The members here are composed of the immunoglobulin (Ig) domain of the collagenase stimulatory factor, basigin-1 (BSG1; also known as Cluster of Differentiation 147 (CD147) and Extracellular Matrix Metalloproteinase Inducer (EMMPRIN)) and similar proteins. CD147 is a transmembrane glycoprotein that belongs to the immunoglobulin superfamily. It is expressed in nearly all cells including platelets and fibroblasts and is involved in inflammatory diseases, and cancer progression. CD147 is highly expressed in several cancers and used as a prognostic marker. The two primary isoforms of CD147 that are related to cancer progression have been identified: CD147 Ig1-Ig2 (also called Basigin-2) that is ubiquitously expressed in most tissues and CD147 Ig0-Ig1-Ig2 (also called Basigin-1) that is retinal specific and implicated in retinoblastoma. Studies showed that CD147 Ig0 domain is a potent stimulator of interleukin-6 and suggest that the CD147 Ig0 dimer is the functional unit required for activity.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 568959839 255 PLQGLTREGDAFELTCEAIGKPQPVMVTW---------------------VRVDDEMPQHAVLSgpnLFINNLNKTDNGT 313
Cdd:cd20940    7 PLSQQRLVGDSVELHCEAVGSPIPEIQWWfegqepneicsqlwdgarldrVHINATYHQHATST---ISIDNLTEEDTGT 83

                 ....*..
gi 568959839 314 YRCEASN 320
Cdd:cd20940   84 YECRASN 90

Immunoglobulin (Ig)-like domain found in Perlecan and similar proteins; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the third immunoglobulin (Ig)-like domain found in Perlecan. Perlecan is a large multi-domain heparin sulfate proteoglycan, important in tissue development and organogenesis. Perlecan can be represented as 5 major portions; its fourth major portion (domain IV) is a tandem repeat of immunoglobulin-like domains (Ig2-Ig15) which can vary in size due to alternative splicing. Perlecan binds many cellular and extracellular ligands. Its domain IV region has many binding sites. Some of these have been mapped at the level of individual Ig-like domains, including a site restricted to the Ig5 domain for heparin/sulfatide, a site restricted to the Ig3 domain for nidogen-1 and nidogen-2, a site restricted to Ig4-5 for fibronectin, and sites restricted to Ig2 and to Ig13-15 for fibulin-2. 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 568959839 261 REGDAFELTCEAIGKPQPVMVTWVRVDDEMPQHAVLSGPNLFINNLNKTDNGTYRCEASN 320
Cdd:cd05754   14 RPGADVSFICRAKSKSPAYTLVWTRVNGTLPSRAMDFNGILTIRNVQLSDAGTYVCTGSN 73

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 568959839 262 EGDAFELTCEAIGKPQPvMVTWVRVDDEMPQHAVLSGPN---LFINNLNKTDNGTYRCEASNIVGKAHSDYMLYV 333
Cdd:cd05876    9 RGQSLVLECIAEGLPTP-TVKWLRPSGPLPPDRVKYQNHnktLQLLNVGESDDGEYVCLAENSLGSARHAYYVTV 82

Second immunoglobulin (Ig)-like domain of a Follistatin-related protein 5, 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 found in human Follistatin-related protein 5 (FSTL5) and a follistatin-like molecule encoded by the CNS-related Mahya gene. Mahya genes have been retained in certain Bilaterian branches during evolution. They are conserved in Hymenoptera and Deuterostomes, but are absent from other metazoan species such as fruit fly and nematode. Mahya proteins are secretory, with a follistatin-like domain (Kazal-type serine/threonine protease inhibitor domain and EF-hand calcium-binding domain), two Ig-like domains, and a novel C-terminal domain. Mahya may be involved in learning and memory and in processing of sensory information in Hymenoptera and vertebrates. Follistatin is a secreted, multidomain protein that binds activins with high affinity and antagonizes their signaling.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 568959839 254 YPLQGLTREGDAFELTCEAIGKPQPvMVTWVR----VDDEMPQHAVL--SGPNLFINNLNKTDNGTYRCEASNIVGKAHS 327
Cdd:cd05736    6 YPEFQAKEPGVEASLRCHAEGIPLP-RVQWLKngmdINPKLSKQLTLiaNGSELHISNVRYEDTGAYTCIAKNEGGVDED 84

                 ....*....
gi 568959839 328 DYMLYVYDT 336
Cdd:cd05736   85 ISSLFVEDS 93

Second immunoglobulin (Ig) domain of nectin-3 and nectin-4 (poliovirus receptor related protein 4), 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 nectin-3 (also known as poliovirus receptor related protein 3 or cluster of differentiation (CD) 113) and nectin-4 (poliovirus receptor related protein 4). Nectin-3 and nectin-4 belong to the nectin family comprised of four transmembrane glycoproteins (nectin-1 through -4). 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. Nectin-3 has also been shown to form a heterophilic trans-interaction with nectin-1 in ciliary epithelia, establishing the apex-apex adhesion between the pigment and non-pigment cell layers. Nectin-4 has recently been identified in several types of breast carcinoma and can be used as a histological and serological marker for breast cancer.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 568959839 161 EGEEIEVNCTAMASKPATTIRWfkgNKELKGKSEVE--EWSDMYTVTSQLMLKVHKEDDGVPVICQVEHPAVtgnLQTQR 238
Cdd:cd07704   16 GNETLAASCTAETGKPAASVTW---ETDLGGMESSRtfEHNRTATVTSEYHLVPTRFANGRPLTCVVSHPAL---QQDIR 89

                 .
gi 568959839 239 Y 239
Cdd:cd07704   90 I 90

Third immunoglobulin domain in Cluster of Differentiation (CD) 22; member of the Constant 2 (C2)-set of IgSF domains; The members here are composed of the third immunoglobulin domain in Cluster of Differentiation (CD) 22 (also known as Siglec-2). CD22, a sialic-acid binding immunoglobulin type-lectin (Siglec) family member, is an inhibitory co-receptor of the B-cell receptor (BCR). The inhibitory function of CD22 and its restricted expression on B cells makes CD22 an attractive target against dysregulated B cells that cause autoimmune diseases and B-cell-derived cancers. CD22 plays a vital role in establishing a baseline level of B-cell inhibition, and thus is an important determinant of homeostasis in humoral immunity. 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. 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 568959839 246 PQVHIQMTyPLQGLTREGDAFELTCE-AIGKPQPVMVTWVRVDDEMPQHAVLSgpnLFINNLNKTDNGTYRCEASNIVGK 324
Cdd:cd20937    1 PKLEIKVT-PSDAIVREGDSVTMTCEvSSSNPEYTTVSWLKDGTSLKKQNTFT---LNLREVTKDQSGKYCCQVSNDVGP 76

                 ...
gi 568959839 325 AHS 327
Cdd:cd20937   77 GRS 79

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

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 568959839 263 GDAFELTCEAIGKPQPVmVTW------------VRVDDEMPQHA-VLSGPNlfINNLNKTDNGTYRCEASNIVGKA-HS 327
Cdd:cd20956   16 GPSVSLKCVASGNPLPQ-ITWtldgfpipesprFRVGDYVTSDGdVVSYVN--ISSVRVEDGGEYTCTATNDVGSVsHS 91

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

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 568959839 251 QMTYPLQGLTREGDAFELTCEAIGKPQPvMVTWVRVDD-------------EMPQHAVLSgpNLFINNLNKTDNGTYRCE 317
Cdd:cd05732    4 KITYLENQTAVELEQITLTCEAEGDPIP-EITWRRATRgisfeegdldgriVVRGHARVS--SLTLKDVQLTDAGRYDCE 80

                         90
                 ....*....|...
gi 568959839 318 ASNIVGKaHSDYM 330
Cdd:cd05732   81 ASNRIGG-DQQSM 92

First immunoglobulin (Ig) domain of contactin-1; member of the I-set of Ig superfamily domains; The members here are composed of the first immunoglobulin (Ig) domain of the neural cell adhesion molecule contactin-1. Contactins are comprised of six Ig domains followed by four fibronectin type III (FnIII) domains anchored to the membrane by glycosylphosphatidylinositol. Contactin-1 is differentially expressed in tumor tissues and may, through a RhoA mechanism, facilitate invasion and metastasis of human lung adenocarcinoma. This group belongs to the I-set of IgSF domains.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 568959839 250 IQMTYPLQGLtrEGDAfELTCEAIGKPQPVMvTWVRVD---DEMPQHAVLSGPNLFINNLNKT-DNGTYRCEASNIVGKA 325
Cdd:cd05849    9 IDTIYPEEST--EGKV-SVNCRARANPFPIY-KWRKNNldiDLTNDRYSMVGGNLVINNPDKYkDAGRYVCIVSNIYGKV 84

                 ..
gi 568959839 326 HS 327
Cdd:cd05849   85 RS 86

Immunoglobulin (Ig)-like domain of titin and similar proteins; The members here are composed of the immunoglobulin (Ig)-like domain found in titin-like proteins and similar proteins. Titin (also called connectin) is a fibrous sarcomeric protein specifically found in vertebrate striated muscle. Titin is a giant protein; 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. It appears to function similarly to an elastic band, keeping the myosin filaments centered in the sarcomere during muscle contraction or stretching. Within the sarcomere, titin is also attached to or is associated with myosin binding protein C (MyBP-C). MyBP-C appears to contribute to the generation of passive tension by titin and like titin has repeated Ig-like and FN-III domains. Also included in this group are worm twitchin and insect projectin, thick filament proteins of invertebrate muscle which also have repeated Ig-like and FN-III domains.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 568959839 261 REGDAFELTCEAIGKPQPVmVTWVRVDDEM--PQHA-VLSGPN---LFINNLNKTDNGTYRCEASNIVGKAHSD 328
Cdd:cd05748    5 RAGESLRLDIPIKGRPTPT-VTWSKDGQPLkeTGRVqIETTASstsLVIKNAKRSDSGKYTLTLKNSAGEKSAT 77