Lysine residue 240 of human serum albumin is involved in high-affinity binding of bilirubin.
Bilirubin can be coupled covalently to albumin by using water-soluble carbodi-imide as coupling reagent. The optimal specificity in the attachment of bilirubin to the high-affinity site on the albumin molecule was obtained by treating an albumin-bilirubin complex with carbodi-imide in low concentrations and for a short period. The product was reduced, carboxymethylated and digested with trypsin. By fractionation on Sephadex G-50 (superfine grade) a peptide fraction containing most of the bilirubin label was isolated. Further purification by paper chromatography gave one peptide, consisting of residues 240-258. The peptide containined a single lysine residue, 240, and had an intact disulphide bridge. The results indicate that bilirubin is bound to lysine residue 240 at its high-affinity site on human serum albumin.
D000596:Amino Acids / Q000032:analysis; D001663:Bilirubin / Q000378:metabolism*; D001665:Binding Sites; D002234:Carbodiimides; D006801:Humans; D008239:Lysine / Q000032:analysis; D012709:Serum Albumin / Q000032:analysis / Q000378:metabolism*
D000596:Amino Acids; D002234:Carbodiimides; D012709:Serum Albumin; D008239:Lysine; D001663:Bilirubin