The ultraviolet endonuclease of bacteriophage T4. Further characterization

The T4 ultraviolet endonuclease was previously shown to produce strand incisions (nicks) in ultraviolet-irradiated DNA on the 5' side of thymine dimers. The present studies demonstrate that the purified endonuclease creates 3'-OH and 5'-P termini at the sites of nicking. Photoreactivation of ultraviolet-sensitive sites, thereby demonstrating directly endonucleause has a molecular weight of approximately 18,000 and attacks ultraviolet-irradiated single-stranded Escherichia coli and M-13 DNA.