The broad host-range plasmid RK2 is able to replicate in and be inherited in a stable manner in diverse Gram-negative bacterial species. It encodes a number of co-ordinately regulated operons including a central control korF1 operon that represses the kfrA operon. The KfrA polypeptide is a site-specific DNA-binding protein whose operator overlaps the kfrA promoter. The N-terminus, containing an helix-turn-helix motif, is essential for function. Downstream from this family is an extended coiled-coil domain containing a heptad repeat segment which is probably responsible for formation of multimers, and may provide an example of a bridge to host structures required for plasmid partitioning [2].

1: Divergence and conservation of the partitioning and global regulation functions in the central control region of the IncP plasmids RK2 and R751. Macartney DP, Williams DR, Stafford T, Thomas CM; Microbiology. 1997;143:2167-2177. PMID:9245806

2: kfrA gene of broad host range plasmid RK2 encodes a novel DNA-binding protein. Jagura-Burdzy G, Thomas CM; J Mol Biol. 1992;225:651-660. PMID:1602476