RAPID REFOLDING STUDIES ON THE CHAPERONE-LIKE ALPHA-CRYSTALLIN - EFFECT OF ALPHA-CRYSTALLIN ON REFOLDING OF BETA-CRYSTALLIN AND GAMMA-CRYSTALLIN

alpha-Crystallin, a multimeric protein present in the eye lens, is shown to have chaperone-like activity in preventing thermally induced aggregation of enzymes and other crystallins, We have studied the rapid refolding of alpha-crystallin, and compared it with other calf eye lens proteins, namely beta- and gamma-crystallins, alpha-Crystallin forms a clear solution upon rapid refolding from 8 M urea, The refolded alpha-crystallin has native-like secondary, tertiary, and quaternary structures as revealed by circular dichroism and fluorescence characteristics as well as gel filtration and sedimentation velocity measurements. On rapid refolding, beta- and gamma-crystallins aggregate and form turbid solutions, The presence of alpha-crystallin in the refolding buffer marginally increases the recovery of beta-and gamma-crystallins in the soluble form, However, unfolding of these crystallins together with alpha-crystallin using 8 M urea and subsequent refolding significantly increases the recovery of these proteins in the soluble form, These results indicate that an intermediate of alpha-crystallin formed during refolding is more effective in preventing the aggregation of beta- and gamma-crystallins, This supports our earlier hypothesis (Raman, B., and Rao, C.M. (1994) J. Biol. Chem. 269, 27264-27268) that the chaperone-like activity of alpha-crystallin is more pronounced in its structurally perturbed state.