Mechanism of suppression of dithiothreitol-induced aggregation of bovine α-lactalbumin by α-crystallin

The kinetics of dithiothreitol (DTT)-induced aggregation of α-lactalbumin from bovine milk has been studied using dynamic light-scattering technique. Analysis of the distribution of the particles formed in the solution of α-lactalbumin after the addition of DTT by size showed that the initial stage of the aggregation process was the stage of formation of the start aggregates with the hydrodynamic radius (Rh) of 80-100 nm. Further growth of the protein aggregates proceeds as a result of sticking of the start aggregates. Suppression of α-lactalbumin aggregation by α-crystallin is mainly due to the increase in the duration of the lag period on the kinetic curves of aggregation. It is assumed that the initially formed complexes of unfolded α-lactalbumin with α-crystallin were transformed to the primary clusters prone to aggregation as a result of the redistribution of the denatured protein molecules on the surface of the α-crystallin particles.