Impact of crowding on aggregation of UV-irradiated βL-crystallin and chaperone like activity of α-crystallin depends of the nature of a crowding agent.

The effect of crowding on the aggregation of UV irradiated βL-crystallin and the chaperone-like activity of α-crystallin has been studied. PEG-20000, BSA and γ-crystallin were used as crowders. It was shown that the initial rate of aggregation of UV irradiated βL-crystallin depended on the type of crowder: the rate did not change in the presence of BSA, doubled when the concentration of γ-crystallin reached 30 mg/ml, and increased linearly with increasing PEG concentration. It was found that PEG is not an inert compound, but causes additional destabilization and denaturation of UV irradiated βL-crystallin. The nucleation time of UV irradiated βL-crystallin aggregation in the presence of BSA and γ-crystallin decreased linearly with an increase in the excluded volume up to 5 %, then remained constant. It was found that BSA and γ-crystallin reduced the initial adsorption capacity of α-crystallin, which was used to quantify chaperone-like activity, in a concentration-dependent manner. g-crystallin demonstrated a greater ability to suppress chaperone-like activity compared to BSA. This difference is due to γ-crystallin ability to interact with α-crystallin. The obtained results indicate the importance of using the exact same crowders that in vivo create the environment of the biochemical process for study in vitro.