The identity of the binding sites of bile salts on bovine serum albumin.

The binding of hydroxy and keto bile salts to bovine serum albumin was studied using probes for the so-called site I, II, bilirubin and fatty acids. Lithocholate, cholanate-3-one and cholanate-3,6-dione produced an interference in the energy transfer process between the albumin-tryptophan residues and the fluorescence markers of sites I and II. The results showed that site II is the binding site for the bile salts on bovine serum albumin. The binding produced a conformational change at site I, bilirubin and fatty acid binding sites, suggesting that these sites may overlap with site II.