groEL and dnaK genes of Escherichia coli are induced by UV irradiation and nalidixic acid in an htpR+-dependent fashion.

Two proteins with molecular weights of 61,000 and 73,000 were found to be induced by UV light in Escherichia coli mutants in which the SOS responses are constitutively expressed. The induction of these proteins by UV light and nalidixic acid was shown to be independent of the recA+ lexA+ regulatory system. Analysis of these proteins by two-dimensional gel electrophoresis and comparison with the "heat-shock" proteins of E. coli revealed that the Mr 61,000 protein comigrated with the groEL gene product, that the Mr 73,000 protein comigrated with the dnaK gene product, and that other heat-shock proteins were also induced. The induction of groEL and dnaK by UV light and nalidixic acid is controlled by the htpR locus. The results suggest that the regulatory response of E. coli to agents such as UV light and nalidixic acid is more complex than previously thought.