Isolation and function of the gene A initiator of bacteriophage phi-chi 174, a highly specific DNA endonuclease

The gene A product of Escherichia coli bacteriophage varphiX 174, necessary for initiation of varphiX DNA synthesis, has been identified and purified to near homogeneity. The gene A protein is shown to be a highly specific DNA endonuclease which breaks one phosphodiester bond in the viral strand of either double-stranded, circular varphiX replicative form I (RFI), or in single-stranded, circular varphiX viral DNA; it is inactive against all other species of DNA tested.