Human lens beta-crystallin solubility

The human lens is composed primarily of water and proteins called crystallins. Insolubility of these crystallins is correlated with aging and cataractogenesis. The alpha-crystallins have chaperone-like activity in maintaining the solubility of denatured beta- and gamma-crystallins. One established test of this chaperone activity is the ability of alpha-crystallin to prevent thermal destabilization of beta-crystallins. Several studies have addressed the effects of structural modifications of alpha-crystallin on chaperone activity, but little is known about the solubilities of the various beta-crystallins or the effects of post-translational modifications. Understanding the solubilities of different forms of beta-crystallins is important to elucidating the mechanism of chaperone activity. In this study, the solubilities of beta-crystallins were examined. The beta-crystallins included the gene products of betaB2, betaA1/A3, betaA4, and betaB1 as well as forms modified in vivo. Analysis of the beta-crystallins by high performance liquid chromatography and mass spectrometry before and after heating revealed large differences in the relative solubilities of the beta-crystallins. These results demonstrate a decreased solubility of specific beta-crystallins and post-translational modifications that may play a role in the crystallin insolubility associated with aging and cataract.