Expression and function of small heat shock protein genes during Xenopus development.

The hsp30 small heat shock protein family is a stress-inducible group of molecular chaperones in the frog, Xenopus laevis. Hsp30 genes are intronless and present in clusters. Expression of these genes are developmentally regulated likely at the level of chromatin structure. Also heat-induced hsp30 transcripts and protein are enriched in selected embryonic tissues. In vitro studies revealed that multimeric hsp30 binds to heat denatured target protein, inhibits their aggregation and maintains them in a folding-competent state until reactivated by other cellular chaperones. Finally optimal chaperone activity and secondary structure of hsp30 can be inhibited by phosphorylation or mutagenesis of the C-terminal end.