Interaction of Hsp27 with native phosphorylase kinase under crowding conditions.

Interaction of the wild type (wt) heat shock protein Hsp27 and its three-dimensional (3D) mutant (mimicking phosphorylation at Ser15, 78, and 82) with rabbit skeletal muscle phosphorylase kinase (PhK) has been studied under crowding conditions modeled by addition of 1 M trimethylamine N-oxide (TMAO). According to the data of sedimentation velocity and dynamic light scattering, crowding provokes the formation of large-sized associates of both PhK and Hsp27. Under crowding conditions, small associates of PhK and Hsp27 interact with each other thus leading to dissociation of large homooligomers of each protein. Taking into account high concentrations of PhK in the cell, we speculate that native PhK might modulate the oligomeric state and chaperone-like activity of Hsp27.