The Thermal Structural Transition of a-Crystallin Inhibits the Heat Induced Self-Aggregation

a-crystallin, the major constituent of human lens, is a member of the heat-shock proteins family and it is known to have a quaternary structural transition at Tc~450C. The presence of calcium ions and/or temperature changes induce supramolecular self-aggregation, a process of relevance in the cataractogenesis. Here we investigate the potential effect of the bovine a-crystallin s structural transition on the self-aggregation process. Along all the temperatures investigated, aggregation proceeds by forming intermediate molecular assemblies that successively aggregate in clusters. The final morphology of the aggregates, above and below Tc, is similar, but the aggregation kinetics are completely different. The size of the intermediate molecular assemblies, and their repulsive energy barrier show a marked increase while crossing Tc. Our results highlight the key role of heat modified form of a-crystallin in protecting from aggregation and preserving the transparency of the lens under hyperthermic conditions