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 1335173376  31 DRGKHFKTSLKVEGEPVVLRCPQARYWLgaTASPRGTVTWRKSGSAVPAPGE-DGRVWVQDGDLWILPAQRGDSGTYLCT 109
Cdd:cd05756     2 EWGEDIKILVVLEGEPDVIKCPLFPNFL--AQSAGLNLTWYKNDSETPISFEpDSRIHQEKDKLWFVPALLEDSGNYYCV 79

                          90
                  ....*....|....*..
gi 1335173376 110 VRNASYCDQMALDLRVL 126
Cdd:cd05756    80 VRNSTYCSKVSISLEVV 96

First immunoglobulin (Ig)-like domain of interleukin-1 receptor (IL1R), and similar domains; The members here are composed of the first immunoglobulin (Ig)-like domain of interleukin-1 receptor (IL1R; also known as cluster of differentiation (CD) 121). IL-1 alpha and IL-1 beta are cytokines which participate in the regulation of inflammation, immune responses, and hematopoiesis. These cytokines bind to the IL-1 receptor type 1 (IL1R1), which is activated on additional association with interleukin-1 receptor accessory protein (IL1RAP). IL-1 also binds a second receptor designated type II (IL1R2). Mature IL1R1 consists of three Ig-like domains, a transmembrane domain, and a large cytoplasmic domain. Mature IL1R2 is organized similarly except that it has a short cytoplasmic domain. The latter does not initiate signal transduction. A naturally occurring cytokine IL-1RA (IL-1 receptor antagonist) is widely expressed and binds to IL-1 receptors, inhibiting the binding of IL-1 alpha and IL-1 beta.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1335173376  31 DRGKHFKTSLKVEGEPVVLRCPQARYWLgaTASPRGTVTWRKSGSAVPAPGE-DGRVWVQDGDLWILPAQRGDSGTYLCT 109
Cdd:cd05756     2 EWGEDIKILVVLEGEPDVIKCPLFPNFL--AQSAGLNLTWYKNDSETPISFEpDSRIHQEKDKLWFVPALLEDSGNYYCV 79

                          90
                  ....*....|....*..
gi 1335173376 110 VRNASYCDQMALDLRVL 126
Cdd:cd05756    80 VRNSTYCSKVSISLEVV 96

Second immunoglobulin (Ig)-like domain of interleukin-1 receptor-2 (IL1R2), and similar domains; The members here are composed of the second immunoglobulin (Ig)-like domain of interleukin-1 receptor-2 (IL1R2). IL-1 alpha and IL-1 beta are cytokines which participate in the regulation of inflammation, immune responses, and hematopoiesis. These cytokines bind to the IL-1 receptor type 1 (IL1R1), which is activated on additional association with interleukin-1 receptor accessory protein (IL1RAP). IL-1 also binds the IL-1 receptor, type II (IL1R2) represented in this group. Mature IL1R2 consists of three IG-like domains, a transmembrane domain, and a short cytoplasmic domain. It lacks the large cytoplasmic domain of mature IL1R1 and does not initiate signal transduction. A naturally occurring cytokine IL-1RA (IL-1 receptor antagonist) is widely expressed and binds to IL-1 receptors, inhibiting the binding of IL-1 alpha and IL-1 beta.

                          10        20        30
                  ....*....|....*....|....*....|....*.
gi 1335173376 136 VSYPQVLTVAASGSLVCPELSEFAKNKTDLKIQWYK 171
Cdd:cd05897     1 ISYPQILFTSTSGKLVCPDLSEFTINRTDVEIQWYK 36

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1335173376  35 HFKTSLKVEGEPVVLRCpqarywlGATASPRGTVTWRKSGSAV-PAPGEDGRVWVQDGDLWILPAQRGDSGTYLCTVRN 112
Cdd:pfam13927   7 SPSSVTVREGETVTLTC-------EATGSPPPTITWYKNGEPIsSGSTRSRSLSGSNSTLTISNVTRSDAGTYTCVASN 78

First immunoglobulin (Ig)-like domain of interleukin-1 receptor (IL1R), and similar domains; The members here are composed of the first immunoglobulin (Ig)-like domain of interleukin-1 receptor (IL1R; also known as cluster of differentiation (CD) 121). IL-1 alpha and IL-1 beta are cytokines which participate in the regulation of inflammation, immune responses, and hematopoiesis. These cytokines bind to the IL-1 receptor type 1 (IL1R1), which is activated on additional association with interleukin-1 receptor accessory protein (IL1RAP). IL-1 also binds a second receptor designated type II (IL1R2). Mature IL1R1 consists of three Ig-like domains, a transmembrane domain, and a large cytoplasmic domain. Mature IL1R2 is organized similarly except that it has a short cytoplasmic domain. The latter does not initiate signal transduction. A naturally occurring cytokine IL-1RA (IL-1 receptor antagonist) is widely expressed and binds to IL-1 receptors, inhibiting the binding of IL-1 alpha and IL-1 beta.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1335173376  31 DRGKHFKTSLKVEGEPVVLRCPQARYWLgaTASPRGTVTWRKSGSAVPAPGE-DGRVWVQDGDLWILPAQRGDSGTYLCT 109
Cdd:cd05756     2 EWGEDIKILVVLEGEPDVIKCPLFPNFL--AQSAGLNLTWYKNDSETPISFEpDSRIHQEKDKLWFVPALLEDSGNYYCV 79

                          90
                  ....*....|....*..
gi 1335173376 110 VRNASYCDQMALDLRVL 126
Cdd:cd05756    80 VRNSTYCSKVSISLEVV 96

Second immunoglobulin (Ig)-like domain of interleukin-1 receptor-2 (IL1R2), and similar domains; The members here are composed of the second immunoglobulin (Ig)-like domain of interleukin-1 receptor-2 (IL1R2). IL-1 alpha and IL-1 beta are cytokines which participate in the regulation of inflammation, immune responses, and hematopoiesis. These cytokines bind to the IL-1 receptor type 1 (IL1R1), which is activated on additional association with interleukin-1 receptor accessory protein (IL1RAP). IL-1 also binds the IL-1 receptor, type II (IL1R2) represented in this group. Mature IL1R2 consists of three IG-like domains, a transmembrane domain, and a short cytoplasmic domain. It lacks the large cytoplasmic domain of mature IL1R1 and does not initiate signal transduction. A naturally occurring cytokine IL-1RA (IL-1 receptor antagonist) is widely expressed and binds to IL-1 receptors, inhibiting the binding of IL-1 alpha and IL-1 beta.

                          10        20        30
                  ....*....|....*....|....*....|....*.
gi 1335173376 136 VSYPQVLTVAASGSLVCPELSEFAKNKTDLKIQWYK 171
Cdd:cd05897     1 ISYPQILFTSTSGKLVCPDLSEFTINRTDVEIQWYK 36

First immunoglobulin (Ig)-like domain of interleukin-1 receptor (IL1R), and similar domains; The members here are composed of the first immunoglobulin (Ig)-like domain of interleukin-1 receptor (IL1R). IL-1 alpha and IL-1 beta are cytokines which participate in the regulation of inflammation, immune responses, and hematopoiesis. These cytokines bind to the IL-1 receptor type 1 (IL1R1), which is activated on additional association with interleukin-1 receptor accessory protein (IL1RAP). IL-1 also binds a second receptor designated type II (IL1R2). Mature IL1R1 consists of three Ig-like domains, a transmembrane domain, and a large cytoplasmic domain. Mature IL1R2 is organized similarly except that it has a short cytoplasmic domain. The latter does not initiate signal transduction. IL-1 receptor antagonist (IL-1RA), a naturally occurring cytokine, is widely expressed and binds to IL-1 receptors, inhibiting the binding of IL-1 alpha and IL-1 beta.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|...
gi 1335173376  65 RGTVTWRKSGSAVPAPGE-DGRVWVQDGDLWILPAQRGDSGTYLCTVRNASYCDQMALDLRVL 126
Cdd:cd20991    29 KGTITWYKNDSKTPISMEqDSRIHQYKEKLWFVPAKVEDSGHYYCVVRNSTYCLKIKITAKFV 91

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1335173376  35 HFKTSLKVEGEPVVLRCpqarywlGATASPRGTVTWRKSGSAV-PAPGEDGRVWVQDGDLWILPAQRGDSGTYLCTVRN 112
Cdd:pfam13927   7 SPSSVTVREGETVTLTC-------EATGSPPPTITWYKNGEPIsSGSTRSRSLSGSNSTLTISNVTRSDAGTYTCVASN 78

Immunoglobulin I-set domain;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|..
gi 1335173376  43 EGEPVVLRCPqarywlgATASPRGTVTWRKSGSAVPaPGEDGRVWVQDGD--LWILPAQRGDSGTYLCTVRN 112
Cdd:pfam07679  14 EGESARFTCT-------VTGTPDPEVSWFKDGQPLR-SSDRFKVTYEGGTytLTISNVQPDDSGKYTCVATN 77

Fifth Ig-like domain of Roundabout (Robo) homolog 1/2, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fifth Ig-like domain of Roundabout (Robo) homolog 1/2 and similar domains. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, -2, and -3), and three mammalian Slit homologs (Slit-1,-2, -3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, -2, and -3 are expressed by commissural neurons in the vertebrate spinal cord and Slits 1, -2, -3 are expressed at the ventral midline. Robo-3 is a divergent member of the Robo family which instead of being a positive regulator of slit responsiveness, antagonizes slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit2 has been shown by surface plasmon resonance experiments and mutational analysis to be is the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site. The fifth Ig-like domain of Robo 1 and 2 is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1335173376  15 FTIQPEERTVAAGSCqdrgkhfktslkvegepVVLRCPqarywlgATASPRGTVTWRKSGsaVPAPGEDGRVWVQD-GDL 93
Cdd:cd20952     2 ILQGPQNQTVAVGGT-----------------VVLNCQ-------ATGEPVPTISWLKDG--VPLLGKDERITTLEnGSL 55

                          90       100
                  ....*....|....*....|.
gi 1335173376  94 WILPAQRGDSGTYLCTVRNAS 114
Cdd:cd20952    56 QIKGAEKSDTGEYTCVALNLS 76

agrin-responsive first immunoglobulin-like domains (Ig1) of the MuSK ectodomain; a member of the I-set of IgSF domains; The members here are composed of the first immunoglobulin-like domains (Ig1) of the Muscle-specific kinase (MuSK). MuSK is a receptor tyrosine kinase specifically expressed in skeletal muscle, where it plays a central role in the formation and maintenance of the neuromuscular junction (NMJ). MuSK is activated by agrin, a neuron-derived heparan sulfate proteoglycan. The activation of MUSK in myotubes regulates the formation of NMJs through the regulation of different processes including the specific expression of genes in subsynaptic nuclei, the reorganization of the actin cytoskeleton and the clustering of the acetylcholine receptors (AChR) in the postsynaptic membrane. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of the MuSK lacks this strand and thus it belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 1335173376  43 EGEPVVLRCpqarywlGATASPRGTVTWRKSGSaVPAPGEDGRVWVQDGD-LWILPAQRGDSGTYLCTVRN 112
Cdd:cd20970    16 EGENATFMC-------RAEGSPEPEISWTRNGN-LIIEFNTRYIVRENGTtLTIRNIRRSDMGIYLCIASN 78

Fifth 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 fifth 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 1335173376  42 VEGEPVVLRCPQARYwlgatasPRGTVTWRKSGSAVPapgEDGRVWV-QDGDLWILPAQRG-DSGTYLCTVRN 112
Cdd:cd20958    13 VAGQTLRLHCPVAGY-------PISSITWEKDGRRLP---LNHRQRVfPNGTLVIENVQRSsDEGEYTCTARN 75

First immunoglobulin (Ig)-like domain of X-linked interleukin-1 receptor accessory protein-like 1 (IL1RAPL-1), and similar domains; The members here are composed of the first immunoglobulin (Ig)-like domain of X-linked interleukin-1 receptor accessory protein-like 1 (IL1RAPL-1). IL-1 alpha and IL-1 beta are cytokines which participate in the regulation of inflammation, immune responses, and hematopoiesis. These cytokines bind to the IL-1 receptor type 1 (IL1R1), which is activated on additional association with interleukin-1 receptor accessory protein (IL1RAP). IL-1 also binds a second receptor designated type II (IL1R2). Mature IL1R1 consists of three Ig-like domains, a transmembrane domain, and a large cytoplasmic domain. Mature IL1R2 is organized similarly except that it has a short cytoplasmic domain. The latter does not initiate signal transduction. A naturally occurring cytokine IL-1RA (IL-1 receptor antagonist) is widely expressed and binds to IL-1 receptors, inhibiting the binding of IL-1 alpha and IL-1 beta. IL1RAPL is encoded by a gene on the X-chromosome, this gene is wholly or partially deleted in multiple cases of non-syndromic intellectual disability. This group also contains IL1RAPL-2 which is also encoded by a gene on the X-chromosome and is a candidate for another non-syndromic intellectual disability loci.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1335173376  36 FKTSLKVEGEPVVLRCP------QARYWLGATASPRgtVTWRKSGSAV----PAPGEDGRVWVQDGDLWILPAQRGDSGT 105
Cdd:cd05896     7 LKKYMVLAGEPVRIKCAlfygyiRTNYSMAQSAGLS--LMWYKSSGPGdfeePIIFDGVRMSKEEDSIWFRPAELQDSGL 84

                          90       100
                  ....*....|....*....|
gi 1335173376 106 YLCTVRNASYCDQMALDLRV 125
Cdd:cd05896    85 YTCVLRNSTYCMKVSMSLTV 104

Fourth immunoglobulin (Ig)-like domain of L1, Ng-CAM (Neuron-glia CAM cell adhesion molecule), and NrCAM (Ng-CAM-related); The members here are composed of the fourth immunoglobulin (Ig)-like domain of L1, Ng-CAM (Neuron-glia CAM cell adhesion molecule), and NrCAM (Ng-CAM-related). These proteins belong to the L1 subfamily of cell adhesion molecules (CAMs) and are comprised of an extracellular region having six Ig-like domains and five fibronectin type III domains, a transmembrane region and an intracellular domain. These molecules are primarily expressed in the nervous system. 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.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 1335173376  43 EGEPVVLRCpqarywlGATASPRGTVTWRKSGSAVPAPGEDGRVWVqDGDLWILPA-QRGDSGTYLCTVRN 112
Cdd:cd04978    13 PGETGELIC-------EAEGNPQPTITWRLNGVPIEPAPEDMRRTV-DGRTLIFSNlQPNDTAVYQCNASN 75

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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1335173376  37 KTSLKVEGEPVVLRC-PQArywlgataSPRGTVTWRKSGSAVPapgEDGRVWV-QDGDLWILPAQRGDSGTYLCTVRN 112
Cdd:cd04969    10 KKILAAKGGDVIIECkPKA--------SPKPTISWSKGTELLT---NSSRICIlPDGSLKIKNVTKSDEGKYTCFAVN 76

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 1335173376  43 EGEPVVLRCPqarywlgATASPRGTVTWRKSGSAVPAPGEDGRVWV-QDGDLWILPAQRGDSGTYLCTVRNASYCDQMAL 121
Cdd:cd20969    16 EGHTVQFVCR-------ADGDPPPAILWLSPRKHLVSAKSNGRLTVfPDGTLEVRYAQVQDNGTYLCIAANAGGNDSMPA 88

                  ....
gi 1335173376 122 DLRV 125
Cdd:cd20969    89 HLHV 92

Fourth immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM); The members here are composed of the fourth immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM). L1 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.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1335173376  44 GEPVVLRCPqarywlgATASPRGTVTWRKSGSAVPAPGEDGRVWVQDGDLWILPAQRGDSGTYLCTVRN 112
Cdd:cd05867    14 GETARLDCQ-------VEGIPTPNITWSINGAPIEGTDPDPRRHVSSGALILTDVQPSDTAVYQCEARN 75

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
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 1335173376  64 PRGTVTWRKSGSAVpapGEDGRVWVQDGD----LWILPAQRGDSGTYLCTVRNASYCDQMALDLRV 125
Cdd:cd05748    20 PTPTVTWSKDGQPL---KETGRVQIETTAsstsLVIKNAKRSDSGKYTLTLKNSAGEKSATINVKV 82

Fourth immunoglobulin (Ig)-like domain in Robo (roundabout) receptors; member of the I-set of Ig superfamily (IgSF) domains; Members here are composed the fourth immunoglobulin (Ig)-like domain in Robo (roundabout) receptors. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, Robo2, Robo3), and three mammalian Slit homologs (Slit-1, Slit-2, Slit-3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, Robo2, and Robo3 are expressed by commissural neurons in the vertebrate spinal cord and Slit-1, Slit-2, and Slit-3 are expressed at the ventral midline. Robo-3 is a divergent member of the Robo family which instead of being a positive regulator of Slit responsiveness, antagonizes Slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit2 has been shown by surface plasmon resonance experiments and mutational analysis to be the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site. This group belongs to the I-set of IgSF domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1335173376  15 FTIQPEERTVAagscqdrgkhfktslkvEGEPVVLRCPqarywlgATASPRGTVTWRKSGSAV-----PAPGEDGRVWV- 88
Cdd:cd05726     2 FVVKPRDQVVA-----------------LGRTVTFQCE-------TKGNPQPAIFWQKEGSQNllfpyQPPQPSSRFSVs 57

                          90       100
                  ....*....|....*....|
gi 1335173376  89 QDGDLWILPAQRGDSGTYLC 108
Cdd:cd05726    58 PTGDLTITNVQRSDVGYYIC 77

Second immunoglobulin (Ig)-like domain of interleukin-1 receptor (IL1R), and similar domains; The members here are composed of the second immunoglobulin (Ig)-like domain of interleukin-1 receptor (IL1R). IL-1 alpha and IL-1 beta are cytokines which participate in the regulation of inflammation, immune responses, and hematopoiesis. These cytokines bind to the IL-1 receptor type 1 (IL1R1), which is activated on additional association with interleukin-1 receptor accessory protein (IL1RAP). IL-1 also binds a second receptor designated type II (IL1R2). Mature IL1R1 consists of three IG-like domains, a transmembrane domain, and a large cytoplasmic domain. Mature IL1R2 is organized similarly except that it has a short cytoplasmic domain. The latter does not initiate signal transduction. A naturally occurring cytokine IL-1RA (IL-1 receptor antagonist) is widely expressed and binds to IL-1 receptors, inhibiting the binding of IL-1 alpha and IL-1 beta. This group also contains ILIR-like 1 (IL1R1L) which maps to the same chromosomal location as IL1R1 and IL1R2.

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gi 1335173376 138 YPQVLTVAASGSLVCPELsEFAKNKTD--LKIQWYK 171
Cdd:cd20994     3 YKQKVPFTSGGRIVCPHL-DFFKDENNnlPKVQWYK 37