Bilirubin binding by the fractionated alternate allelic components of heterozygous monkey albumin.

Analysis of bilirubin-binding parameters for purified albumin of nine rhesus monkeys heterozygous for albumin MacA and albumin MacB was performed after separating these two albumin forms by fast protein liquid chromatography (FPLC). The binding capacity (n) for MacA-enriched samples was lower than that for the MacB variant in eight of nine fraction pairs analyzed, while the affinity constant (K) was higher in all nine MacA-enriched samples. The values for n X K were higher in MacA-enriched samples in eight of nine pairs tested. These data, together with previous studies, geographic specificity of the MacB variant, and the presence of dietary competitors for the primary bilirubin binding site on the albumin molecule, suggest an evolutionary advantage for the MacB variant only in areas where the dietary competitors are present.