Temperature-induced exposure of hydrophobic surfaces and its effect on the chaperone activity of α-crystallin

Abstract

α-Crystallin, the major protein of the ocular lens, is known to have extensive similarities to small heat shock proteins and to act as a molecular chaperone. The exposure of hydrophobic surfaces on α-crystallin was studied by fluorescence spectroscopy using the hydrophobic probe bis-ANS. Upon heating the protein undergoes a conformational transition which is associated with a marked increase in surface hydrophobicity. This transition, which occurs between approximately 38 and 5-°C, lacks reversibility. The increase in surface hydrophobicity correlates with the increased chaperone activity of the protein. These results indicate that hydrophobic interactions play a major role in the chaperone action of α-crystallin.