Identification of a seventh operon on plasmid RK2 regulated by the korA gene product

Broad-host-range IncP plasmids possess a series of operons involved in plasmid maintenance, whose expression is coordinated by a series of regulators, most of which are encoded in a central regulatory operon. The nucleotide sequence of a new monocistronic operon located between coordinates 55.0 and 56.0 kb on the genome of the IncP alpha plasmids RK2 and RP4 is presented. The operon encodes a 34 kDa protein which has a net negative charge. Transcription of the operon, designated by us kfrA (korF-regulated), is repressed not only by the product of the previously described korA gene but also by the product of a gene which we have designated korF and which has not been described previously. The korF gene is encoded downstream from korB within the key korA/korB regulatory operon. We propose that K or F binds to a novel inverted repeat overlapping the promoter for the kfrA operon.