Js. Lee et al., ALPHA-CRYSTALLIN ACTING AS A MOLECULAR CHAPERONIN AGAINST PHOTODAMAGEBY UV IRRADIATION, Journal of protein chemistry, 16(4), 1997, pp. 283-289
alpha-Crystallin, a major protein of the eye lens, is known to have ch
aperone activity in preventing heat-induced aggregation of enzymes and
other crystallins. In this study, we investigate the ability of alpha
-crystallin to inhibit UV-light-induced aggregation of other lens prot
eins and the effect of exposure of alpha-crystallin to UV irradiation
on its chaperone activity. The chaperone activities of alpha-crystalli
n preincubated at different temperatures were found to be different an
d could be correlated with its change in quaternary structure as deter
mined by the fluorescence probe ANS (8-anilo-1-naphthalene sulfonate).
alpha-Crystallin can inhibit the aggregation of gamma-crystallin from
UV irradiation at room temperature, and the preheated alpha-crystalli
ns provide more protection than the native one. Upon irradiation by UV
light, alpha-crystallin gradually lost its ability to protect beta-cr
ystallin against thermal aggregation. The loss of the chaperone effica
cy of alpha-crystallin to protect other lens proteins may shed light o
n human cataract formation induced by long-term exposure to UV irradia
tion.