CONFORMATIONAL-CHANGES IN 17 CYSTINE DISULFIDE BRIDGES OF BOVINE SERUM-ALBUMIN PROVED BY RAMAN-SPECTROSCOPY

Conformational changes in cystine disulfide bridges of bovine serum al bumin during acid-induced isomerization (N-->F and F --> E transitions ) have been studied with Raman spectroscopy, In an X-ray crystallograp hic study of human serum albumin, Carter and Ho reported that all disu lfide bridges of the albumin molecule are in the gauche-gauche-gauche conformation [1], On the other hand, the solution structure of bovine serum albumin examined by Raman spectroscopy differs from its crystal structure in the conformation of some of the disulfide bridges, Two Ra man bands were detected at 520 and 505 cm(-1) in the disulfide stretch ing mode region, suggesting that the 17 disulfide bridges in the N-for m of bovine serum albumin solution take both the gauche-gauche-gauche and gauche-gauche-trans conformations, The ratio of the peak intensiti es at 520 and 505 cm(-1) (I-505/I-520) is increased from 1.6 to 2.1 an d from 2.1 to 6.3 on going from the N- to the F-form and from the F- t o the E-form, respectively, indicating that the gauche-gauche-trans co nformation of the disulfide bridges is converted to a gauche-gauche-ga uche one which is the most energetically stable form during the acid-i nduced isomerization, However, small amounts of gauche-gauche-trails c onformation still remain even in the E-form. (C) 1997 Federation of Eu ropean Biochemical Societies.