A novel single strand endonuclease specific for ØX174 DNA

A highly specific endonuclease activity, presumably involving one or both of the products of the ØX174 gene A, has been isolated from ØX174-infected $\text{E. coli}$ by DNA-cellulose chromatography. The enzyme is not present in uninfected cells and binds extremely tightly to DNA-cellulose. It extensively degrades ØX174 viral DNA but does not degrade the circular or linear forms of single stranded viral DNA of either M13, an unrelated filamentous phage, or G4, a ØX-type phage.