title: Molecular cloning of S-protein, a link between complement, coagulation and cell-substrate adhesion.
abstract: cDNA clones coding for human S-protein have been isolated using monoclonal antibodies to screen a cDNA library in pEX. These clones are shown to be authentic S-protein clones on the basis of sequence, composition and immunological criteria. The complete open reading frame sequence for S-protein has been determined and shows it to be a single polypeptide chain of 459 amino acids preceded by a cleaved leader peptide of 19 residues. No evidence was found for polymorphism of S-protein suggesting that different molecular weight forms arise by proteolytic degradation. Of the first 44 amino-terminal residues 42 are identical with the so-called somatomedin B peptide suggesting that S-protein is the somatomedin B precursor. Striking homology is found in the rest of the sequence with the serum spreading factor, vitronectin, which has also been shown to contain somatomedin B sequences at its amino terminus. We conclude that S-protein and vitronectin are identical and discuss the relevance of this finding to the coagulation and complement pathways.
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D003001:Cloning, Molecular; D003165:Complement System Proteins / Q000235:genetics; D004247:DNA / Q000302:isolation & purification; D004262:DNA Restriction Enzymes; D005796:Genes; D006023:Glycoproteins / Q000235:genetics*; D006801:Humans; D008099:Liver / Q000378:metabolism; D008562:Membrane Glycoproteins; D011485:Protein Binding; D019096:Vitronectin
chemical_list: D000596:Amino Acids; D000911:Antibodies, Monoclonal; D003165:Complement System Proteins; D004247:DNA; D004262:DNA Restriction Enzymes; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D019096:Vitronectin