Abstract
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.
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