Novel rpoA mutation that interferes with the function of OmpR and EnvZ, positive regulators of the ompF and ompC genes that code for outer-membrane proteins in Escherichia coli K12.

The expression of the ompF and ompC genes that code for major outer-membrane proteins of Escherichia coli is positively regulated by the products of the ompR and envZ genes. Recently, we isolated the ompR77 mutation, which suppresses the envZ11 mutation. In this work, a novel mutation that interferes with the suppression of the envZ11 mutation by ompR77 was isolated. The mutation was located in the rpoA gene that codes for the alpha subunit of DNA-dependent RNA polymerase. These results suggest that an interaction between the positive regulators and RNA polymerase is involved in the initiation of transcription of the ompF and ompC genes. In addition, the results suggest that during transcription the RNA polymerase migrates along DNA strands with the alpha subunit facing backward and the beta beta' subunits facing forward.