The differenciatl sensitivity of lens alpha A- and alpha B-crystallin to UV B irradiation

Abstract

Lens alpha crystallin consists of large aggregates of two molecules, alpha A- and alpha B-crystallin. The present study focused on the differential sensitivity of these two crystallins to UV-B irradiation. Alpha A- and alpha B-crystallins were studied by circular dichroism spectrum analysis, analytical ultracentrifugation and Bis-ANS fluorescence spectra following UV-B irradiation at 10, 20, 30, 40 or 50 J/cm². Sedimentation coefficients of alpha A-crystallin aggregates increased and their distribution became heterogeneous after UV-B irradiation above 30 J/cm². In addition, the chaperone activity of alpha A-crystallin dramatically decreased following irradiation. However, the size of alpha B-crystallin aggregates did not change and retained its chaperone activity after UV-B irradiation even up to 50 J/cm². The present study indicates that alpha A-crystallin is more susceptible to UV-B irradiation than alpha B-crystallin. This may be one of the reasons why alpha-crystallin consists of both alpha A- and alpha B-crystallin molecules.