Calpain-induced light scattering by crystallins from three rodent species

The purpose of the present investigation was to compare in vitro light scattering in the soluble proteins from rodent lenses after hydrolysis by the calcium-activated protease, m-calpain (EC 3.4.22.17). Light scattering was measured in solutions of lens proteins from mice, rats, and guinea pigs after activation of endogenous m-calpain or after addition of purified m-calpain. We found for the first time that, in addition to rat, crystallins from another rodent lens, young mouse, were susceptible to calpain-induced light scattering. As in rats, aging of mouse lens prevented calpain-induced light scattering. Although crystallins from guinea pig lens were also partially hydrolysed by calpain, appreciable light scattering did not occur. Limited proteolysis may cause common changes in the biophysical properties of mouse and rat crystallins to decrease their solubility. Discovery of the nature of these biophysical changes may help our understanding as to why crystallins precipitate under cataractous conditions.