Improvement of protein stability and enzyme recovery under stress conditions by using a small HSP (tpv-HSP 14.3) from Thermoplasma volcanium

In this study we cloned and expressed a small heat shock protein, tpv-HSP 14.3, from thermoacidophilic archaeon Thermoplasma volcanium. This novel recombinant small heat shock protein was purified to homogeneity and produced a protein band of 14.3 kDa on SDS-polyacrylamide gel. Transmission electron microscopy images of the negatively stained tpv-HSP 14.3 samples showed spherical particles of 13 nm diameter. E. coli cells over expressing tpv-HSP 14.3 endowed the cells with some degree of thermotolerance. After exposure to 52 °C for 120 min, survivability of the E. coli cells expressing tpv-HSP 14.3 was approximately 2.5-fold higher than the control cells. As a molecular chaperone tpv-HSP 14.3 enhanced the thermal stabilization of substrate proteins, pig heart citrate synthase and bovine l-glutamic dehdyrogenase, considerably. The highest protection effect of tpv-HSP 14.3 was observed at 47 °C for pig heart citrate synthase; the remaining activity was 5-fold higher than that of the sample without tpv-HSP 14.3. The tpv-sHSP 14.3 prevented inactivation of bovine l-glutamic dehdyrogenase the most effectively at 53 °C; the residual activity was approximately 2-fold higher than that of the sample heated without tpv-HSP 14.3. However, refolding activity of the tpv-HSP 14.3 was relatively weak for the chemically denatured substrate proteins.