The groE gene products of Escherichia coli are dispensable for mucA+B(+)-dependent UV mutagenesis.

UV mutagenesis in Escherichia coli requires the groES+EL+ chaperonins as well as the umuD+C+ SOS-regulated genes. GroES and GroEL appear to be required to stabilize UmuC. The mucA+B+ genes, which are encoded on a broad host range plasmid, are functionally analogous and structurally similar to the umuD+C+ genes of E. coli. While these gene pairs are quite similar, differences have been reported in the functioning of these gene products. We tested whether mucA+B+ function requires the groE+ gene products as well. We show that mucA+B(+)-induced UV mutagenesis, UV resistance, phage reactivation and cold sensitivity do not require the groE+ heat shock genes. These findings suggest that the requirement of UmuC for groES+EL+ function is not shared by its analog, MucB.