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Abstract The deoxyribonuclease controlled by the recB and recC loci of Escherichia coli K-12 has been purified to near homogeneity. It is composed of two nonidentical polypeptide chains with a combined molecular weight of approximately 270,000. In the presence of ATP the enzyme hydrolyzes linear duplex or single stranded DNA in an exonucleolytic manner to 5'-phosphoryl-terminated oligonucleotides of an average length of 4.5. The enzyme can also cleave single stranded DNA endonucleolytically, being stimulated 7-fold by ATP in this reaction. However, no nuclease activity is observed on closed circular duplex DNA. In the course of exonuclease digestion more than 20 ATP molecules are hydrolyzed to ADP and inorganic phosphate for each DNA phosphodiester bond broken. There is no ATP hydrolysis in the absence of degradable DNA.
Goldmark et al. (Wed,) studied this question.