Hidden self-association of proteins

✍ Scribed by Nobuhiro Muramatsu; Allen P. Minton

• Publisher: John Wiley and Sons
• Year: 1989
• Tongue: English
• Weight: 620 KB
• Volume: 1
• Category: Article
• ISSN: 0952-3499
• DOI: 10.1002/jmr.300010404

✦ Synopsis

Sedimentation equilibrium measurements were carried out on solutions of bovine serum albumin, aldolase, and ovalbumin in phosphate-buffered saline, pH 7.2, at 10°C. The data obtained for each protein were analyzed to yield the dependence of apparent weight-average molecular weight upon protein concentration, over a concentration range of ca 1-200 g/L. Using the approximate theory of Chatelier and Minton ((1987) Biopolymers 26, 507-524), models are formulated for the dependence of apparent weight-average molecular weight upon concentration in non-ideal solutions containing proteins which may self-associate according to a monomer/n-mer or a monomer/dimer/tetramer scheme.

The concentration dependence data for serum albumin may be accounted for, assuming either no self-association or weak monomer/dimer association. The data for aldolase may be accounted for assuming either weak monomer/dimer or weak monomer/trimer association. The data for ovalbumin may be accounted for assuming either weak monomer/ trimer or weak monomer/dimer/tetramer association. The associations do not approach saturation at the highest concentrations studied, and the standard-state free energy changes accompanying self-association amount to less than 4 kcal/mol of intermolecular contacts, suggesting that non-specific clustering of protein molecules a t high concentration rather than the formation of specific complexes is being observed.