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 1039759608  35 KVTQPEKSVSVAAGDSTVLNCTLTSLLPVGPIRWYRGVGPSRLLIYSFAGEYVPRIRNVSDTTKRNNMDFSIRISNVTPA 114
Cdd:cd16097     1 QVIQPEKSVSVAAGESATLHCTVTSLIPVGPIQWFRGAGPGRELIYNQKEGHFPRVTTVSDLTKRNNMDFSIRISNITPA 80

                          90       100       110
                  ....*....|....*....|....*....|..
gi 1039759608 115 DAGIYYCVKFQKGSSePDTEIQSGGGTEVYVL 146
Cdd:cd16097    81 DAGTYYCVKFRKGSP-DDVEFKSGAGTELSVR 111

Immunoglobulin (Ig)-like variable (V) domain of the Signal-Regulatory Protein (SIRP); The members here are composed of the immunoglobulin (Ig)-like domain of the Signal-Regulatory Protein (SIRP). 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 that contain either ITIMs or transmembrane regions 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 with much less affinity. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039759608  35 KVTQPEKSVSVAAGDSTVLNCTLTSLLPVGPIRWYRGVGPSRLLIYSFAGEYVPRIRNVSDTTKRNNMDFSIRISNVTPA 114
Cdd:cd16097     1 QVIQPEKSVSVAAGESATLHCTVTSLIPVGPIQWFRGAGPGRELIYNQKEGHFPRVTTVSDLTKRNNMDFSIRISNITPA 80

                          90       100       110
                  ....*....|....*....|....*....|..
gi 1039759608 115 DAGIYYCVKFQKGSSePDTEIQSGGGTEVYVL 146
Cdd:cd16097    81 DAGTYYCVKFRKGSP-DDVEFKSGAGTELSVR 111

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

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039759608   41 KSVSVAAGDSTVLNCTLTSLlPVGPIRWYRGvgPSRLLIYSfageyvPRIrnvsdTTKRNNMDFSIRISNVTPADAGIYY 120
Cdd:smart00410   2 PSVTVKEGESVTLSCEASGS-PPPEVTWYKQ--GGKLLAES------GRF-----SVSRSGSTSTLTISNVTPEDSGTYT 67

                           90       100
                   ....*....|....*....|....*.
gi 1039759608  121 C-VKFQKGSSEpdteiqsgGGTEVYV 145
Cdd:smart00410  68 CaATNSSGSAS--------SGTTLTV 85

Immunoglobulin (Ig)-like variable (V) domain of the Signal-Regulatory Protein (SIRP); The members here are composed of the immunoglobulin (Ig)-like domain of the Signal-Regulatory Protein (SIRP). 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 that contain either ITIMs or transmembrane regions 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 with much less affinity. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039759608  35 KVTQPEKSVSVAAGDSTVLNCTLTSLLPVGPIRWYRGVGPSRLLIYSFAGEYVPRIRNVSDTTKRNNMDFSIRISNVTPA 114
Cdd:cd16097     1 QVIQPEKSVSVAAGESATLHCTVTSLIPVGPIQWFRGAGPGRELIYNQKEGHFPRVTTVSDLTKRNNMDFSIRISNITPA 80

                          90       100       110
                  ....*....|....*....|....*....|..
gi 1039759608 115 DAGIYYCVKFQKGSSePDTEIQSGGGTEVYVL 146
Cdd:cd16097    81 DAGTYYCVKFRKGSP-DDVEFKSGAGTELSVR 111

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 1039759608  38 QPEKSVSVAAGDSTVLNCTLTSL--LPVGPIRWYRG--VGPSRLLIYSFAGEYVPRIR--NVSDTTKRNNMDFSIRISNV 111
Cdd:pfam07686   1 QTPREVTVALGGSVTLPCTYSSSmsEASTSVYWYRQppGKGPTFLIAYYSNGSEEGVKkgRFSGRGDPSNGDGSLTIQNL 80

                          90       100       110
                  ....*....|....*....|....*....|....*
gi 1039759608 112 TPADAGIYYCVKFqkgssePDTEIQSGGGTEVYVL 146
Cdd:pfam07686  81 TLSDSGTYTCAVI------PSGEGVFGKGTRLTVL 109

Immunoglobulin (Ig) light chain, kappa type, variable (V) domain; The members here are composed of the immunoglobulin (Ig) light chain, kappa type, variable (V) domain. This group contains the standard Ig superfamily V-set AGFCC'C"/DEB domain topology. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. There are two types of light chains: kappa and lambda, each composed of a constant domain (CL) and a variable domain (VL). There are five types of heavy chains (alpha, gamma, delta, epsilon, and mu), which determines the type of immunoglobulin formed: IgA, IgG, IgD, IgE, and IgM, respectively. In higher vertebrates, there are two types of light chain, designated kappa and lambda, which seem to be functionally identical, and can associate with any of the heavy chains.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039759608  36 VTQPEKSVSVAAGDSTVLNCTLTSLLPVGPIRWY--RGVGPSRLLIYS-----------FAGEYvprirnvSDTtkrnnm 102
Cdd:cd04980     3 MTQSPASLSVSPGERVTISCKASQSISSNYLAWYqqKPGQAPKLLIYYastlhsgvpsrFSGSG-------SGT------ 69

                          90       100       110       120
                  ....*....|....*....|....*....|....*....|.
gi 1039759608 103 DFSIRISNVTPADAGIYYCvkfQKGSSEPDTeiqSGGGTEV 143
Cdd:cd04980    70 DFTLTISSVEPEDAAVYYC---QQGYTFPYT---FGGGTKL 104

Immunoglobulin (Ig) variable (V) domain of T-cell receptor (TCR) gamma chain; The members here are composed of the immunoglobulin (Ig) variable (V) domain of the gamma chain of gamma/delta T-cell receptors (TCRs). TCRs mediate antigen recognition by T lymphocytes, and are heterodimers consisting of alpha and beta chains or gamma and delta chains. Each chain contains a variable (V) and a constant (C) region. The majority of T cells contain alpha/beta TCRs, but a small subset contain gamma/delta TCRs. Alpha/beta TCRs recognize antigens as peptide fragments presented by major histocompatibility complex (MHC) molecules. Gamma/delta TCRs recognize intact protein antigens directly without antigen processing and recognize MHC independently of the bound peptide. Gamma/delta T cells can also be stimulated by non-peptide antigens such as small phosphate- or amine-containing compounds. The variable domain of gamma/delta TCRs is responsible for antigen recognition and is located at the N-terminus of the receptor. Members of this group contain the standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039759608  36 VTQPEKSVSVAAGDSTVLNCTLTSL-LPVGPIRWYR---GVGPSRLLIYSfageYVPRIRNVSDTTK--------RNNMD 103
Cdd:cd04982     1 LEQPQLSITREESKSVTISCKVSGIdFSTTYIHWYRqkpGQALERLLYVS----STSAVRKDSGKTKnkfearkdVGKST 76

                          90       100
                  ....*....|....*....|....*.
gi 1039759608 104 FSIRISNVTPADAGIYYCVKFQKGSS 129
Cdd:cd04982    77 STLTITNLEKEDSATYYCAYWESGSG 102

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 1039759608  36 VTQPEKSVSVAAGDSTVLNCTLTSLLP--VGPIRWYRGVGPSRLLI--------YSFAGEYVPRIRNVSDTTKRNNMdfS 105
Cdd:cd05718     2 RVQVPTEVTGFLGGSVTLPCSLTSPGTtkITQVTWMKIGAGSSQNVavfhpqygPSVPNPYAERVEFLAARLGLRNA--T 79

                          90       100       110
                  ....*....|....*....|....*....|
gi 1039759608 106 IRISNVTPADAGIYYC--VKFQKGSSEPDT 133
Cdd:cd05718    80 LRIRNLRVEDEGNYICefATFPQGNRQGTT 109

Immunoglobulin (Ig) lambda light chain variable (V) domain; The members here are composed of the immunoglobulin (Ig) light chain, lambda type, variable (V) domain. The basic structure of Ig molecules is a tetramer of two light chains and two heavy chains linked by disulfide bonds. There are two types of light chains: kappa and lambda, each composed of a constant domain (CL) and a variable domain (VL). There are five types of heavy chains (alpha, gamma, delta, epsilon, and mu), which determines the type of immunoglobulin formed: IgA, IgG, IgD, IgE, and IgM, respectively. In higher vertebrates, there are two types of light chain, designated kappa and lambda, which seem to be functionally identical, and can associate with any of the heavy chains. Members of this group contain standard Ig superfamily V-set AGFCC'C"/DEB domain topology.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039759608  36 VTQPEkSVSVAAGDSTVLNCTLTSLLPVGP-IRWYRGVGPS--RLLIY--SFAGEYVP-RIRNVSDTTKRnnmdfSIRIS 109
Cdd:cd04984     2 LTQPS-SLSVSPGETVTITCTGSSGNISGNyVNWYQQKPGSapRYLIYedKHRPSGIPdRFSGSKSGNTA-----SLTIS 75

                          90       100       110
                  ....*....|....*....|....*....|....*.
gi 1039759608 110 NVTPADAGIYYCVKFQKGSsepdteIQSGGGTEVYV 145
Cdd:cd04984    76 GAQTEDEADYYCQVWDSNS------YVFGGGTKLTV 105

Immunoglobulin (Ig)-like domain of myelin oligodendrocyte glycoprotein (MOG); The members here are composed of the immunoglobulin (Ig)-like domain of myelin oligodendrocyte glycoprotein (MOG). MOG, a minor component of the myelin sheath, is an important CNS-specific autoantigen, linked to the pathogenesis of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). It is a transmembrane protein having an extracellular Ig domain. MOG is expressed in the CNS on the outermost lamellae of the myelin sheath, and on the surface of oligodendrocytes, and may participate in the completion, compaction, and/or maintenance of myelin. This group also includes butyrophilin (BTN). BTN is the most abundant protein in bovine milk-fat globule membrane (MFGM).

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039759608  35 KVTQPEKSVSVAAGDSTVLNCTLTsllpvgP--------IRWYRGvGPSRL-LIY----SFAGEYVPRIRN----VSDTT 97
Cdd:cd05713     2 SVIGPTEPILALVGEDAELPCHLS------PkmsaehmeVRWFRS-QFSPVvHLYrdgqDQEEEQMPEYRGrtelLKDAI 74

                          90       100       110
                  ....*....|....*....|....*....|..
gi 1039759608  98 KRNNMdfSIRISNVTPADAGIYYCVkFQKGSS 129
Cdd:cd05713    75 AEGSV--ALRIHNVRPSDEGQYTCF-FRSGSF 103

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039759608  35 KVTQPEKSVSVAAGDSTVLNCTLTSLlPVGPIRWYRG---VGPSRLLiysfageyvpRIRNVSDTTkrnnmdfSIRISNV 111
Cdd:pfam07679   2 KFTQKPKDVEVQEGESARFTCTVTGT-PDPEVSWFKDgqpLRSSDRF----------KVTYEGGTY-------TLTISNV 63

                          90
                  ....*....|.
gi 1039759608 112 TPADAGIYYCV 122
Cdd:pfam07679  64 QPDDSGKYTCV 74

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

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039759608  39 PEKSVSVAAGDSTVLNCtLTSLLPVGPIRWYRGVGPsrlliysfageyVPrirnvSDTTKRNNMDFSIRISNVTPADAGI 118
Cdd:cd05731     1 SESSTMVLRGGVLLLEC-IAEGLPTPDIRWIKLGGE------------LP-----KGRTKFENFNKTLKIENVSEADSGE 62

                  ....
gi 1039759608 119 YYCV 122
Cdd:cd05731    63 YQCT 66

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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 1039759608  52 VLNCTLTSLlPVGPIRWYRGvgpsrlliysfaGEYVPRIRNVSDTTKRNNmdFSIRISNVTPADAGIYYCV 122
Cdd:cd00096     2 TLTCSASGN-PPPTITWYKN------------GKPLPPSSRDSRRSELGN--GTLTISNVTLEDSGTYTCV 57

First immunoglobulin (Ig) variable (V) domain of rat MRC OX-2 antigen, and similar domains; The members here are composed of the first immunoglobulin (Ig) domain of rat MRC OX-2 antigen (also known as CD200) and similar proteins. MRC OX-2 is a membrane glycoprotein expressed in a variety of lymphoid and non-lymphoid cells in rats. It has a similar broad distribution pattern in humans. MRC OX-2 may regulate myeloid cell activity. The protein has an extracellular portion containing two Ig-like domains, a transmembrane portion, and a cytoplasmic portion.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039759608  33 ELKVTQPEksvSVAAGDSTVLNCTLTSLLPVGPIRWYR--GVGPSRLLIYS------FAGEYVPRIRnvsdTTKRNNMDF 104
Cdd:cd05846     1 VVVHTGDT---RAVLGGNATLSCNLTLPEEVLQVTWQKikASSPENIVTYSkkygvkIQPSYVRRIS----FTSSGLNST 73

                          90
                  ....*....|....*..
gi 1039759608 105 SIRISNVTPADAGIYYC 121
Cdd:cd05846    74 SITIWNVTLEDEGCYKC 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        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039759608  36 VTQPEKSVSVAAGDSTVLNCTLTSLLPVGPIRWYRGVGPsrlliysfageyVPRirnvsdttkrNNMDFS--IRISNVTP 113
Cdd:cd05754     4 TVEEPRSQEVRPGADVSFICRAKSKSPAYTLVWTRVNGT------------LPS----------RAMDFNgiLTIRNVQL 61

                  ....*....
gi 1039759608 114 ADAGIYYCV 122
Cdd:cd05754    62 SDAGTYVCT 70

Immunoglobulin (Ig)-like domain of protein zero (P0) and similar proteins; The members here are composed of the immunoglobulin (Ig) domain of protein zero (P0), a myelin membrane adhesion molecule. P0 accounts for over 50% of the total protein in peripheral nervous system (PNS) myelin. P0 is a single-pass transmembrane glycoprotein with a highly basic intracellular domain and an extracellular Ig domain. The extracellular domain of P0 (P0-ED) is similar to the Ig variable domain, carrying one acceptor sequence for N-linked glycosylation. P0 plays a role in membrane adhesion in the spiral wraps of the myelin sheath. The intracellular domain is thought to mediate membrane apposition of the cytoplasmic faces and may, through electrostatic interactions, interact directly with lipid headgroups. It is thought that homophilic interactions of the P0 extracellular domain mediate membrane juxtaposition in the extracellular space of PNS myelin. This group also contains the Ig domain of sodium channel subunit beta-2 (SCN2B), and of epithelial V-like antigen 1 (EVA). EVA, also known as myelin protein zero-like 2, is an adhesion molecule, which may play a role in structural organization of the thymus and early lymphocyte development. SCN2B subunits play a role in determining sodium channel density and function in neurons,and in control of electrical excitability in the brain.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1039759608  34 LKVTQPeKSVSVAAGDSTVLNCTLTSLLPVG---PIRW-YR--GVGPSRLLIYSFAGEYVP--------RIRNVSDTTKR 99
Cdd:cd05715     1 MEVYTP-RELNVLNGSDVRLTCTFTSCYTVGdafSVTWtYQpeGGNTTESMFHYSKGKPYIlkvgrfkdRVSWAGNPSKK 79

                          90       100
                  ....*....|....*....|..
gi 1039759608 100 nnmDFSIRISNVTPADAGIYYC 121
Cdd:cd05715    80 ---DASIVISNLQFSDNGTYTC 98