Lens alpha-crystallin, alphaA- and alphaB-crystallin, and Hsp27 are members of the small heat shock protein family. Both CXA- and alphaB-crystallin are expressed in the lens and serve as structural proteins and as chaperones, but aB-crystallin is also expressed in nonlenticular organs where Hsp27, rather than alphaA-crystallin, is expressed along with alphaB-crystallin. It is not known what additional function Hsp27 has besides as a heat shock protein, but it may serve, as alphaA-crystallin does in the lens, to stabilize alphaB-crystallin. In this study, we investigate aspects on conformation and thermal stability for the mixture of Hsp27 and alphaB-crystallin. Size exclusion chromatography, circular dichroism (M), and light scattering measurements indicated that Hsp27 prevented alphaB-crystallin from heat-induced structural changes and high molecular weight (HMW) aggregation. The results indicate that Hsp27 indeed promotes stability of alphaB-crystallin. (C) 2003 Elsevier Science (USA). All rights reserved.