Kinetics of thermal aggregation of glycogen phosphorylase b from rabbit skeletal muscle: Mechanism of protective action of α‐crystallin

The kinetics of thermal aggregation of glycogen phosphorylase b (Ph b ) from rabbit skeletal muscle have been studied by dynamic light scattering (0.08 M Hepes, pH 6.8, containing 0.1 M NaCl; 48°C). The hydrodynamic radius of the start aggregates determined from the initial linear parts of the dependences of the hydrodynamic radius ( R h ) on time was found to be 16.7 ± 1.0 nm. At rather high values of time, the R h value for the protein aggregates becomes proportional to t 1/1.8 = t 0.56 suggesting that the aggregation process proceeds in the regime of diffusion‐limited cluster–cluster aggregation. In the presence of α‐crystallin, a protein possessing the chaperone‐like activity, the process of protein aggregation switches to the regime of reaction‐limited cluster–cluster aggregation as indicated by the exponential dependence of the R h value on time. It was shown that the addition of α‐crystallin raises the rate of thermal inactivation of Ph b . These data in combination with the results of the study of interaction of Ph b with α‐crystallin by analytical ultracentrifugation suggest that α‐crystallin interacts with the intermediates of unfolding of the Ph b molecule. © 2007 Wiley Periodicals, Inc. Biopolymers 89: 124–134, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com