A mutant in a major heat shock protein of Escherichia coli continues to show inducible thermotolerance.

Escherichia coli cells carrying the dnaK756 mutation, were inactivated at 52 degrees C faster than control cells. This suggests that the intact dnaK gene product plays a role in protecting the cell from lethal damage at 52 degrees C. The effect of the dnaK mutation on induced thermotolerance was examined. Prior heat shock at 42 degrees C greatly lowered the subsequent inactivation rate in both mutant and control cells. This result suggests that, although produced in large amounts in response to thermal stress, mutation in the DnaK protein has little or no effect on induced thermotolerance.