REDUCTION AND REOXIDATION OF DISULFIDE BONDS OF BOVINE SERUM ALBUMIN

The disulfide bonds of bovine serum albumin (BSA) were reduced by various methods. On reduction with 0.3 m mercaptoethanol in 8 m urea or 6 m guanidinium hydrochloride at pH 9.0 complete reduction was attained. Reoxidation by air of completely reduced BSA yielded a product which contained considerable amounts of polymers as shown by gel-filtration experiments. The monomer fraction had the same elution volume and sedimentation coefficient as native serum albumin but differed from it with respect to optical rotation, pH-solubility properties, and tryptophan fluorescence. On reoxidation in solutions containing long-chain fatty acids there was less polymer formation. pH-solubility fractionation of the monomer showed that it contained about 80% of material with the same optical rotation, pH-solubility properties, tryptophan fluorescence, and binding properties as native serum albumin. These results can be taken as an indication that the formation of the tertiary structure of BSA during its biosynthesis is influenced by lipids which are bound to it. © 1969.