Transient transformation of oligomeric structure of alpha-crystallin during its chaperone action.

New evidence for dynamic behavior and flexible oligomeric structure of the molecular chaperone α-crystallin is presented. Based on the results of laser dynamic light scattering, centrifugal ultrafiltration, size exclusion chromatography, analytical ultracentrifugation and electrophoresis in polyacrylamide gel, addition of α-crystallin to fully reduced α-lactalbumin, used as a model protein substrate, at the stage of its start aggregate formation results in dissociation of multimeric structure of α-crystallin. In addition to large oligomers, transient low-sized assemblies are formed with the apparent molecular mass of 50-55 kDa that corresponds to the α-crystallin dimeric form associated with destabilized monomeric α-lactalbumin. This phenomenon is suggested to represent an essential component of a transient protective mechanism tuning the stressed protein to binding sites on the exposed surface of the chaperone dimers.