The mechanism of the interaction of α-crystallin and UV-damaged β-crystallin.

α-Crystallin maintains the transparency of the lens by preventing the aggregation of damaged proteins. The aim of our work was to study the chaperone-like activity of native α-crystallin in near physiological conditions (temperature, ionic power, pH) using UV-damaged β-crystallin as the target protein. α-Crystallin in concentration depended manner inhibits the aggregation of UV-damaged β-crystallin. DSC investigation has shown that refolding of denatured UV-damaged β-crystallin was not observed under incubation with α-crystallin. α-Crystallin and UV-damaged β-crystallin form dynamic complexes with masses from 75 to several thousand kDa. The content of UV-damaged β-crystallin in such complexes increases with the mass of the complex. Complexes containing >10% of UV-damaged β-crystallin are prone to precipitation whereas those containing <10% of the target protein are relatively stable. Formation of a stable 75 kDa complex is indicative of α-crystallin dissociation. We suppose that α-crystallin dissociation is the result of an interaction of comparable amounts of the chaperone-like protein and the target protein. In the lens simultaneous damage of such amounts of protein, mainly β and gamma-crystallins, is impossible. The authors suggest that in the lens rare molecules of the damaged protein interact with undissociated oligomers of α-crystallin, and thus preventing aggregation.