Abstract
Abstract: :
Purpose. Hsp27 and lens αA- and αB-crystallin are members of the small heat shock protein family. Both αA- and αB-crystallin are expressed in the lens and serve as structural proteins and as chaperones, but αB-crystallin is also expressed in nonlenticular organs where Hsp27, rather than αA-crystallin, is expressed along with αB-crystallin. It is not known what additional function Hsp27 has besides as a heat shock protein. In this study, we investigate aspects of conformation and thermal stability for the mixture of Hsp27 and αB-crystallin. Methods. Human Hsp27 and αB-crystallin were cloned. The effects of Hsp27 on αB-crystallin in conformation and stability were studied by FPLC gel filtration, circular dichroism (CD), and heat-induced unfolding and aggregation. Results. FPLC showed that αB-crystallin was less aggregated by heat in the presence of Hsp27 than in the absence of Hsp27. CD indicated that association of αB-crystallin and Hsp27 protected the structure of αB-crystallin. Light scattering showed that heat-induced aggregation for αB-crystallin decreased with increasing amounts of Hsp27 added to the αB-crystallin solutions. Conclusion. The results indicated that Hsp27 prevented αB-crystallin from heat-induced structural changes and high molecular weight (HMW) aggregation and that Hsp27 promoted stability of αB-crystallin.
Keywords: crystallins • protein structure/function • chaperones