PrfA protein of Bacillus species: prediction and demonstration of endonuclease activity on DNA.

The prfA gene product of Gram-positive bacteria is unusual in being implicated in several cellular processes; cell wall synthesis, chromosome segregation, and DNA recombination and repair. However, no homology of PrfA with other proteins has been evident. Here we report a structural relationship between PrfA and the restriction enzyme PvuII, and thereby produce models that predict that PrfA binds DNA. Indeed, wild-type Bacillus stearothermophilus PrfA, but not a catalytic site mutant, nicked one strand of supercoiled plasmid templates leaving 5'-phosphate and 3'-hydroxyl termini. This activity, much lower on linear or relaxed circular double-stranded DNA or on single-stranded DNA, is consistent with a role for this protein in chromosome segregation, DNA recombination, or DNA repair.