THE A SUBUNIT OF RNA-POLYMERASE SPECIFICALLY INHIBITS EXPRESSION OF THE PORIN GENES OMPF AND OMPC IN-VIVO AND IN-VITRO IN ESCHERICHIA-COLI

Overproduction of the alpha subunit of RNA polymerase in Escherichia c oli resulted in inhibition of transcription of two osmoregulated porin genes, ompF and ompC, but not of constitutively expressed housekeepin g genes. Overproduction of the sigma subunit did not have any inhibito ry effects. The specific inhibitory effect of the alpha subunit was al so found to depend upon the OmpR protein, the transcriptional activato r for ompF and ompC. These results are in general agreement with other biochemical and genetic evidence suggesting that the alpha subunit is the subunit of RNA polymerase that directly interacts with certain tr anscriptional activators to initiate transcription.