High temperature stress resistance of Escherichia coli induced by a tobacco class I low molecular weight heat-shock protein.

TLHS1 is a class I low molecular weight heat-shock protein (LMW HSP) of tobacco (Nicotiana tabacum). For a functional study of TLHS1, a recombinant DNA coding for TLHS1 with a hexahistidine tag at the amino-terminus was constructed and expressed in Escherichia coli. An expressed fusion protein, H6TLHS1, was purified using a Ni2+ affinity column and a Sephacryl S400 HR column. A polyclonal antibody against H6TLHS1 was produced to follow the fate of H6TLHS1 in E. coli. The fusion protein in E. coli maintained its solubility at a temperature of up to 90 degrees C and most of the proteins in the E. coli cell lysate with H6TLHS1 were prevented from thermally induced aggregation at up to 90 degrees C. We compared the viability of E. coli cells expressing H6TLHS1 to the E. coli cells without H6TLHS1 at a temperature of 50 degrees C. After 8 h of high temperature treatment, E. coli cells with H6TLHS1 survived about three thousand times more than the bacterial cells without H6TLHS1. These results showed that a plant class I LMW HSP, TLHS1, can protect proteins of E. coli from heat denaturation, which could lead to a higher survival rate of the bacterial cells at high temperature.