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

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1394767476  24 WSIKVPSDATGEIGKSIVLPCTFTHPHKTFD-RTLTAIWRIKEPYNGTvvFKCVAHSS-SELCKTatSYKNRYKLLGNPR 101
Cdd:cd05712     1 WGLQMPKSVTVQEGLCVLIPCSFSYPADYWVsNPVHGYWYRGGPYPKY--RPPVATNNrTREVHE--STQGRFRLLGDPG 76

                          90       100
                  ....*....|....*....|....*....
gi 1394767476 102 HNNLSIKIDNLTWSDSNRYFCRVEFSGDL 130
Cdd:cd05712    77 KKNCSLSISDARPEDSGKYFFRVERGDSN 105

Immunoglobulin Variable (IgV) domain at the N-terminus of CD33 and related Siglecs (sialic acid-binding Ig-like lectins); The members here are composed of the immunoglobulin (Ig) domain at the N-terminus of Cluster of Differentiation (CD) 33 and related Siglecs (sialic acid-binding Ig-like lectins). Siglec refers to a structurally related protein family that specifically recognizes sialic acid in oligosaccharide chains of glycoproteins and glycolipids. Siglecs are type I transmembrane proteins, 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, the other subgroup is comprised of CD33-related Siglecs which include CD33 (Siglec-3) and human Siglecs 5-11.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1394767476  24 WSIKVPSDATGEIGKSIVLPCTFTHPHKTFD-RTLTAIWRIKEPYNGTvvFKCVAHSS-SELCKTatSYKNRYKLLGNPR 101
Cdd:cd05712     1 WGLQMPKSVTVQEGLCVLIPCSFSYPADYWVsNPVHGYWYRGGPYPKY--RPPVATNNrTREVHE--STQGRFRLLGDPG 76

                          90       100
                  ....*....|....*....|....*....
gi 1394767476 102 HNNLSIKIDNLTWSDSNRYFCRVEFSGDL 130
Cdd:cd05712    77 KKNCSLSISDARPEDSGKYFFRVERGDSN 105

Immunoglobulin (Ig)-like domain of human titin C terminus and similar proteins; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the fifth immunoglobulin (Ig)-like domain from the C-terminus of human titin x and similar proteins. Titin (also called connectin) is a fibrous sarcomeric protein specifically found in vertebrate striated muscle. Titin is gigantic; depending on isoform composition it ranges from 2970 to 3700 kDa, and is of a length that spans half a sarcomere. Titin largely consists of multiple repeats of Ig-like and fibronectin type 3 (FN-III)-like domains. Titin connects the ends of myosin thick filaments to Z disks and extends along the thick filament to the H zone and appears to function similar to an elastic band, keeping the myosin filaments centered in the sarcomere during muscle contraction or stretching. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1394767476 144 LIAAPRiiNITVSSNEDHTFKarCTADGEPLPSLTWtgpLSSNSSSVTSMNHQITKELHHLTHD---------GKYVCTA 214
Cdd:cd05747     6 ILTKPR--SLTVSEGESARFS--CDVDGEPAPTVTW---MREGQIIVSSQRHQITSTEYKSTFEiskvqmsdeGNYTVVV 78

                  ....*...
gi 1394767476 215 ENSHGRAE 222
Cdd:cd05747    79 ENSEGKQE 86

Immunoglobulin V-Type;

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1394767476   39 SIVLPCTFTHphKTFDRTlTAIWRIKEPynGTVVFKCVAHSSSELCKTATSYKNRYKLLGNPRHNNLSIKIDNLTWSDSN 118
Cdd:smart00406   1 SVTLSCKFSG--STFSSY-YVSWVRQPP--GKGLEWLGYIGSNGSSYYQESYKGRFTISKDTSKNDVSLTISNLRVEDTG 75

                   ....
gi 1394767476  119 RYFC 122
Cdd:smart00406  76 TYYC 79

Immunoglobulin Variable (IgV) domain at the N-terminus of CD33 and related Siglecs (sialic acid-binding Ig-like lectins); The members here are composed of the immunoglobulin (Ig) domain at the N-terminus of Cluster of Differentiation (CD) 33 and related Siglecs (sialic acid-binding Ig-like lectins). Siglec refers to a structurally related protein family that specifically recognizes sialic acid in oligosaccharide chains of glycoproteins and glycolipids. Siglecs are type I transmembrane proteins, 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, the other subgroup is comprised of CD33-related Siglecs which include CD33 (Siglec-3) and human Siglecs 5-11.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1394767476  24 WSIKVPSDATGEIGKSIVLPCTFTHPHKTFD-RTLTAIWRIKEPYNGTvvFKCVAHSS-SELCKTatSYKNRYKLLGNPR 101
Cdd:cd05712     1 WGLQMPKSVTVQEGLCVLIPCSFSYPADYWVsNPVHGYWYRGGPYPKY--RPPVATNNrTREVHE--STQGRFRLLGDPG 76

                          90       100
                  ....*....|....*....|....*....
gi 1394767476 102 HNNLSIKIDNLTWSDSNRYFCRVEFSGDL 130
Cdd:cd05712    77 KKNCSLSISDARPEDSGKYFFRVERGDSN 105

Immunoglobulin Variable (IgV) domain of T cell Immunoglobulin Domain and Mucin Domain 3 (Tim-3), and similar domains; The members here are composed of the immunoglobulin variable (IgV) domain of T cell immunoglobulin domain and mucin domain 3 (Tim-3; also known as Hepatitis A virus cellular receptor 2 (HAVcr-2) and Cluster of Differentiation 366 (CD366)) and similar proteins. TIM-3 is a checkpoint inhibitor in immune responses to tumors, as well as involved in chronic viral infections. Thus, Tim-3 has emerged as one of most promising immune checkpoint targets for cancer immunotherapy. Tim-3 is highly expressed on Th1 lymphocytes and CD11b(+) macrophages and is upregulated on activated T and myeloid cells. TIM-3 regulates macrophage, activation and inhibits Th1 mediated immune responses to promote immunological tolerance. There are three TIM family members in humans (TIM-1, TIM-3, and TIM-4) and eight members in mice (TIM-1 to TIM-8). The IgV domain of human TIM-3 has been shown to bind ligands such as carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1), high mobility group protein B1 (HMGB1)and galectin-9 (GAL9). The binding of GAL9 to TIM-3 can negatively regulate Th1 immune response, enhance immune tolerance and inhibit anti#tumor immunity. Dysregulation of the TIM-3/GAL9 pathway is implicated in numerous chronic autoimmune diseases, such as multiple sclerosis and systemic lupus erythematosus.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1394767476  33 TGEIGKSIVLPCTFThphktfdrtltaiwrikEPYNGTVVFKC-------VAHSSSELCKT---ATSYK--NRYKLLGNP 100
Cdd:cd20982     4 RAEVGHNAYLPCSYT-----------------TAAPGNLVPVCwgkgacpVSYCGNVLLRTderDVTYQksSRYQLKGDF 66

                          90       100       110
                  ....*....|....*....|....*....|...
gi 1394767476 101 RHNNLSIKIDNLTWSDSNRYFCRVEFSGDLHDK 133
Cdd:cd20982    67 SKGDVSLTIENVTLADSGIYCCRIQIPGIMNDE 99

First immunoglobulin variable (IgV) domain of poliovirus receptor (PVR, also known as CD155 and necl-5), and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of poliovirus receptor (PVR, also known as CD155 and nectin-like protein 5 (necl-5)). 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), that result from alternate splicing of the CD155 mRNA, and have identical extracellular domains. CD155-beta and CD155-gamma are secreted; 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" with a footprint similar to that of the intercellular adhesion molecule-1 receptor on human rhinoviruses. This group also includes the first Ig-like domain of nectin-1 (also known as poliovirus receptor related protein(PVRL)1; CD111), nectin-3 (also known as PVRL 3), nectin-4 (also known as PVRL4; LNIR receptor)and DNAX accessory molecule 1 (DNAM-1; CD226).

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1394767476  26 IKVPSDATGEIGKSIVLPCTFTHPHKTfdrTLTAI-WRIKEPYNGTVVfkcVAHSSSELCKTATSYKNRYKLLGNP-RHN 103
Cdd:cd05718     3 VQVPTEVTGFLGGSVTLPCSLTSPGTT---KITQVtWMKIGAGSSQNV---AVFHPQYGPSVPNPYAERVEFLAARlGLR 76

                          90       100
                  ....*....|....*....|.
gi 1394767476 104 NLSIKIDNLTWSDSNRYFCRV 124
Cdd:cd05718    77 NATLRIRNLRVEDEGNYICEF 97

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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 1394767476 167 CTADGEPLPSLTW---TGPLSSNSSSVtsMNHQITKELHHLTH--DGKYVCTAENSHGRAEGAVY 226
Cdd:cd05876    17 CIAEGLPTPTVKWlrpSGPLPPDRVKY--QNHNKTLQLLNVGEsdDGEYVCLAENSLGSARHAYY 79

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 1394767476 146 AAPRII---NITVSSNEDHTFKarCTADGEPLPSLTWTGPLSSNSSSVTSMNHQITKELHH-----------LTHDGKYV 211
Cdd:cd05732     1 VQPKITyleNQTAVELEQITLT--CEAEGDPIPEITWRRATRGISFEEGDLDGRIVVRGHArvssltlkdvqLTDAGRYD 78

                          90
                  ....*....|....*.
gi 1394767476 212 CTAENSHGRAEGAVYF 227
Cdd:cd05732    79 CEASNRIGGDQQSMYL 94

Immunoglobulin (Ig)-like I-set domain of Neural Cell Adhesion Molecule 1 (NCAM-1); The members here are composed of the fourth Ig domain of Neural Cell Adhesion Molecule 1(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. 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 1394767476 146 AAPRII---NITVSSNEDHtFKARCTADGEPLPSLTWTGPLSSNSSSVTSMNHQITKELH-----------HLTHDGKYV 211
Cdd:cd05869     1 AKPKITyveNQTAMELEEQ-ITLTCEASGDPIPSITWRTSTRNISSEEKTLDGHIVVRSHarvssltlkyiQYTDAGEYL 79

                          90
                  ....*....|....*.
gi 1394767476 212 CTAENSHGRAEGAVYF 227
Cdd:cd05869    80 CTASNTIGQDSQSMYL 95

Immunoglobulin Variable (IgV) domain of B7-H4; The members here are composed of the immunoglobulin variable (IgV) domain of B7-H4 (also known as B7-S1, B7x, or Vtcn1). B7-H4 is one of the B7 family of immune-regulatory ligands that act as negative regulators of T cell function; it contains one IgV domain and one IgC domain. The B7-family consists of structurally related cell-surface protein ligands, which bind to receptors on lymphocytes that regulate immune responses. The binding of B7-H4 to unidentified receptors results in the inhibition of TCR-mediated T cell proliferation, cell-cycle progression and IL-2 production. As a co-inhibitory molecule, B7-H4 is widely expressed in tumor tissues and its expression is significantly associated with poor prognosis in human cancers such as glioma, pancreatic cancer, oral squamous cell carcinoma, renal cell carcinoma, and lung cancer.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1394767476  34 GEIGKSIVLPCTFTHPHKTFDRTLTaiWrIKEPYNGTV-VFKcvaHSSSELCKTATSYKNRYKLLGNPRH-NNLSIKIDN 111
Cdd:cd20984     9 GNIGEDGILSCTFTPDIKLSDIVIQ--W-LKEGDSGLVhEFK---EGKDELSRQSPMFRGRTSLFADQVHvGNASLRLKN 82

                          90
                  ....*....|...
gi 1394767476 112 LTWSDSNRYFCRV 124
Cdd:cd20984    83 VQLTDAGTYLCII 95

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1394767476  152 NITVSSNEDHTFkaRCTADGEPLPSLTWTGPLSSNSSSVTSMNHQITKELHHLT-------HDGKYVCTAENSHGRAEGA 224
Cdd:smart00410   3 SVTVKEGESVTL--SCEASGSPPPEVTWYKQGGKLLAESGRFSVSRSGSTSTLTisnvtpeDSGTYTCAATNSSGSASSG 80

                   ..
gi 1394767476  225 VY 226
Cdd:smart00410  81 TT 82

Immunoglobulin Variable (IgV) domain of B7-H2 (B7 homolog 2); The members here are composed of the immunoglobulin variable (IgV) domain of B7-H2 (B7 homolog 2 also known as ICOSL (inducible T cell costimulator ligand) or CD275). B7-H2 is a ligand for the T-cell-specific cell surface receptor ICOS and acts as a costimulatory signal for T-cell proliferation and cytokine secretion. The interaction of ICOS with ICOSL (B7-H2) regulates T cell activation and expansion, is involved in T cell dependent B cell activation, and T-helper cell differentiation. It is a member of the B7 family of immune regulatory proteins and shares homology with other B7 ligands, such as B7-1, B7-2, B7-H1 (PD-L1), PD-L2, and B7-H3. The extracellular domains of B7 proteins contain two Ig-like domains and all members have short cytoplasmic domains. These ligands are typically expressed on antigen presenting cells (such as macrophages, B cells and dendritic cells) and have the ability to regulate T-cell proliferation and function. Tumor cells are also capable of expressing the B7 family members in order to evade immune surveillance.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1394767476  36 IGKSIVLPCTftHPHKT-FD-RTLTAIWRIKEPynGTVVFKCVAHSSSeLCKTATSYKNRYKL-LGNPRHNNLSIKIDNL 112
Cdd:cd20935     7 VGSDVELSCI--CPEGSrFDlNDLYVYWQISES--ETVVTYHLPQNSS-LENVDSHYRNRALLsLDSMKQGDFSLRLFNV 81

                          90       100       110
                  ....*....|....*....|....*....|..
gi 1394767476 113 TWSDSNRYFCRVeFSGDLHDKYEGRTGIRLHL 144
Cdd:cd20935    82 TPQDEQKFHCLV-FSQSLELQKVLEVVVTLHV 112

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

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1394767476 151 INITVSSNEDHTFKarCTADGEPLPSLTWT---GPLSSNSSSVTSMNHQIT-----KELhhlthDGKYVCTAENSHGRAE 222
Cdd:cd20978     9 KNVVVKGGQDVTLP--CQVTGVPQPKITWLhngKPLQGPMERATVEDGTLTiinvqPED-----TGYYGCVATNEIGDIY 81

                  ....
gi 1394767476 223 GAVY 226
Cdd:cd20978    82 TETL 85

Immunoglobulin I-set domain of the Leucine-rich repeat and immunoglobin-like domain-containing protein 1 (Lingo-1); The members here are composed of the immunoglobulin I-set (IgI) domain of the Leucine-rich repeat and immunoglobin-like domain-containing protein 1 (Lingo-1). Human Lingo-1 is a central nervous system-specific transmembrane glycoprotein also known as LERN-1, which functions as a negative regulator of neuronal survival, axonal regeneration, and oligodendrocyte differentiation and myelination. Lingo-1 is a key component of the Nogo receptor signaling complex (RTN4R/NGFR) in RhoA activation responsible for some inhibition of axonal regeneration by myelin-associated factors. The ligand-binding ectodomain of human Lingo-1 contains a bimodular, kinked structure composed of leucine-rich repeat (LRR) and immunoglobulin (Ig)-like modules. Diseases associated with Lingo-1 include mental retardation, autosomal recessive 64 and essential tremor. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of the Lingo-1 lacks this strand and thus it belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1394767476 148 PRIiNITVSSNEDHTFKARCTADGEPLPSLTWTGPLSSNSSSVTSMNHQI----TKELHHL--THDGKYVCTAENSHGRA 221
Cdd:cd20969     6 DRK-AQQVFVDEGHTVQFVCRADGDPPPAILWLSPRKHLVSAKSNGRLTVfpdgTLEVRYAqvQDNGTYLCIAANAGGND 84

                  .
gi 1394767476 222 E 222
Cdd:cd20969    85 S 85