Abstract
A rapid synthesis and accumulation of small heat shock proteins (sHSPs) upon heat-shock is one of the important cellular responses in heat stressed higher plants. However, function of plant sHSP remains unclear at present. In the present study, we have shown that ER-sHSP confers thermal protection of other proteins in vitro.
Tomato endoplasmic reticulum-located sHSP (ER-sHSP) cDNA (LeHSP21.4) was successfully cloned. Northern-blot analysis revealed the heat-inducible character of LeHSP21.4 mRNA. To use the recombinant LeHSP21.4, the molecular chaperone function of ER-sHSP was confirmed in vitro. The recombinant LeHSP21.4 was able to enhance the renaturation of chemically denatured lactate dehydrogenase (LDH) and citrate synthase (CS). The protein prevented the thermal aggregation and inactivation of CS at 45oC. Most of proteins of E. coli cell extracts containing the ER-sHSP were protected from heat-denatured precipitation, whereas extracts from cells not expressing the protein were very heat-sensitive at these conditions.
