title: Peptide and nucleotide sequences of rat CD4 (W3/25) antigen: evidence for derivation from a structure with four immunoglobulin-related domains.
abstract: The rat W3/25 antigen was the first marker antigen of helper T lymphocytes to be identified. Subsequently, the human OKT4 antigen (now called CD4) was described, and cell distribution and functional data suggested that W3/25 and OKT4 antigens were homologous. This is now confirmed by the matching of peptide sequences from W3/25 antigen with sequence predicted from rat cDNA clones detected by cross-hybridization with a cDNA probe for human CD4. Analysis of the two sequences suggests an evolutionary origin from a structure with four immunoglobulin-related domains, although only domain 1 at the NH2 terminus meets the standard criteria for an immunoglobulin-related sequence. CD4 domains 2 and 4 contain disulfide bonds but seem like truncated immunoglobulin domains, whereas domain 3 may have a pattern of beta-strands like an immunoglobulin variable domain, but without the disulfide bond.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface / Q000032:analysis* / Q000235:genetics / Q000302:isolation & purification; D001483:Base Sequence; D004247:DNA / Q000032:analysis; D006801:Humans; D007136:Immunoglobulins / Q000032:analysis*; D051381:Rats; D011919:Rats, Inbred Strains; D011971:Receptors, Immunologic / Q000032:analysis; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface; D007136:Immunoglobulins; D011971:Receptors, Immunologic; D004247:DNA