Amino acid sequence of human plasma alpha 1B-glycoprotein: homology to the immunoglobulin supergene family

摘要: The complete amino acid sequence has been determined for alpha 1B-glycoprotein (alpha 1B), a protein of unknown function present in human plasma. This (Mr approximately equal to 63,000) consists single polypeptide chain N-linked four glucosamine oligosaccharides. five intrachain disulfide bonds and contains 474 residues. Analysis the by several computer programs shows that 1B exhibits internal duplication repeating structural domains, each containing about 95 acids one bond. unique sequence. However, domains 1B, especially third, show statistically significant homology variable regions certain immunoglobulin light heavy chains. also similarity other members supergene family such as receptor transepithelial transport IgA IgM secretory component IgA. Because its immunoglobulin-like proteins, appears have evolved from an ancestral gene similar family.