Enzymatic Breakage of Deoxyribonucleic Acid

Abstract

Abstract An endonuclease activity was purified about 150-fold from T4 phage-infected Escherichia coli B. This enzyme has been named T4 endonuclease IV and introduces breaks preferentially into single stranded DNA. The enzyme produces oligonucleotides as small as 150 nucleotides long from fd DNA. These oligonucleotides contain 3'-hydroxyl and 5'-phosphate termini. T4 endonuclease IV produces breaks exclusively adjacent to cytosine residues in both fd and denatured λ DNA. This enzyme has no effect on denatured T4 DNA, whether glucosylated or nonglucosylated, and may therefore be involved in the breakdown of host cell DNA which occurs after T4 phage infection.