Single-Stranded Deoxyribonucleic Acid-specific Nuclease from Vaccinia Virus

A deoxyribonuclease was extracted from vaccinia virus cores and purified 200-fold by chromatography on DEAE-cellulose, DNA-cellulose, and hydroxyapatite. Approximately 0.35 mg of enzyme was isolated from 63 mg of cores. Preparations of [3H]leucine-labeled deoxyribonuclease appeared nearly homogeneous as judged by gel filtration and had a molecular weight of 50,000 as determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The molecular weight of the native enzyme determined by sucrose gradient sedimentation and filtration through Sephadex G-200 was 105,000, suggesting that it may exist as a dimer. The enzyme hydrolyzed single-stranded DNA most actively at pH 4.4 and did not require divalent cations.