Characterization of mitochondria-located small heat shock protein from tomato (Lycopersicon esculentum)

We cloned and sequenced a full-length cDNA encoding the precursor of the mitochondria-located small heat shock protein (MT-sHSP) gene (LeHSP23.8) from tomato (Lycopersicon esculentum). The deduced protein precursor with a calculated molecular weight of 23.8 kDa was predicted to target mitochondria and was classified as a plant MT-sHSP. A single copy of LeHSP23.8 was found in tomato genomic DNA by southern-blot analysis. Northern-blot analysis revealed the heat inducible character of LeHSP23.8 mRNA. The LeHSP23.8 mRNA was hardly detectable at about 36 degrees C but accumulated markedly at 40 degrees C. The molecular chaperone function of LeHSP23.8 was confirmed in vitro. The recombinant LeHSP23.8 was able to enhance the renaturation of chemically denatured citrate synthase (CS). Moreover, the recombinant LeHSP23.8 protected CS from thermal inactivation and also promoted the renaturation of thermally inactivated citrate synthase.