The mode of chaperoning of dithiothreitol-denatured alpha-lactalbumin by alpha-crystallin

Molecular chaperones prevent the aggregation of partially folded or misfold ed forms of protein. alpha-crystallin performs such a function in the ocula r lens. To gain insight into the mechanism of the anti-aggregation activity of alpha-crystallin, we performed dynamic light scattering(DLS) measuremen ts investigating its interaction with partially denatured alpha-lactalbumin over a 24 hr period. Analyses were conducted as a function of the concentr ation of alpha-lactalbumin as well, as the bovine alpha-crystallin/alpha-la ctalbumin ratio. Additional studies of the systems were performed by HPLC a nd SDS gel electrophoresis. The particle distribution patterns derived from the DLS data indicated that the chaperoned complex (lactalbumin plus cryst allin) is a loose fluffy globular entity. After the complex becomes saturat ed with lactalbumin, it appears to release the partially denatured lactalbu min which may aggregate into high molecular weight moieties. These eventual ly may precipitate out of solution. On longer standing, 24hr and over, the chaperoned complex as well as the lactalbumin aggregates become more compac t. The chaperoned complex (alpha-crystallin plus alpha-lactalbumin) is in d ynamic equilibrium both with the monomeric and the aggregated alpha-lactalb umin population. (C) 1999 Academic Press.