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

Molecular chaperones prevent the aggregation of partially folded or misfolded forms of protein. α-crystallin performs such a function in the ocular lens. To gain insight into the mechanism of the anti-aggregation activity of α-crystallin, we performed dynamic light scattering (DLS) measurements investigating its interaction with partially denatured α-lactalbumin over a 24 hr period. Analyses were conducted as a function of the concentration of α-lactalbumin as well as the bovine α-crystallin/α-lactalbumin ratio. Additional studies of the systems were performed by HPLC and SDS gel electrophoresis. The particle distribution patterns derived from the DLS data indicated that the chaperoned complex (lactalbumin plus crystallin) is a loose fluffy globular entity. After the complex becomes saturated with lactalbumin, it appears to release the partially denatured lactalbumin which may aggregate into high molecular weight moieties. These eventually may precipitate out of solution. On longer standing, 24 hr and over, the chaperoned complex as well as the lactalbumin aggregates become more compact. The chaperoned complex (α-crystallin plus α-lactalbumin) is in dynamic equilibrium both with the monomeric and the aggregated α-lactalbumin population.