Abstract: Acting as molecular chaperones, heat shock proteins (Hsps) could help fixing denatured proteins and preventing aggregation of other proteins. In order to better understand the function of molecular chaperones of Hsp families in the parasitoid Pteromalus puparum, Pphsp90, Pphsp70, Pphsc70, Pphsp60, Pphsp40 and Pphsp20 genes from this parasitoid were over-expressed in Escherichia coli. The results showed that the five genes except Pphsp40 were highly expressed and these expressed recombinant Pphsps were soluble and stable under high temperature (80℃). In vivo experiments, Pphsp20 and Pphsp90 significantly increased the survival rate of E. coli cells under high temperature (50℃, 1 h). In vitro protection study verified that only purified recombinant Pphsp20 could reduce the aggregation of luciferase under high temperature. The results suggest that both Pphsp20 and Pphsp90 may be involved in thermo-protective role in E. coli, and Pphsp20 may work independently while Pphsp90 requires the cooperation with other cofactors.

Key words: Pteromalus puparum, heat shock proteins, gene expression, protein thermo-stability, protein purification