Js. Lee et al., EFFECT OF HEAT-INDUCED STRUCTURAL PERTURBATION OF SECONDARY AND TERTIARY STRUCTURES ON THE CHAPERONE ACTIVITY OF ALPHA-CRYSTALLIN, Biochemical and biophysical research communications, 237(2), 1997, pp. 277-282
alpha-Crystallin, a major protein of the lens, is known to have chaper
one activity to protect other proteins against thermal aggregation. He
at-induced structural change of alpha-crystallin was previously shown
to increase its chaperone activity. In this report, we studied the the
rmal reversibility of alpha-crystallin and the effect of change in sec
ondary structure on its chaperone function in vitro. The heat-induced
conformational changes in the aromatic region of near-UV CD spectra sh
owed only a small degree of reversibility. The structural transitions
from 50 to 70 degrees C were largely reversible if the incubation time
was short. However, the protective ability to inhibit thermal aggrega
tion of alcohol dehydrogenase by alpha-crystallin was essentially simi
lar at 48 and 70 degrees C, Under long-term heating at high temperatur
es, there was a time-dependent irreversibility of structural change in
alpha-crystallin as revealed by CD spectroscopy. Such denatured alpha
-crystallin by long-term heating can still preserve its ability to pre
vent UV-induced aggregation of gamma-crystallin at room temperature, i
ndicating relatively little effect of heat-induced changes in secondar
y structure on the chaperone activity of alpha-crystallin. (C) 1997 Ac
ademic Press.