Biochemical and genetic studies of recombination proficiency in Escherichia coli. I. Enzymatic activity associated with recB+ and recC+ genes.

An adenosine triphosphate-dependent deoxyribonuclease activity has been detected in lysates of recB(+)recC(+) strains. Mutations in recB or recC lead to loss of this activity, suggesting that these two genes determine the nuclease activity. The over-all reaction in crude lysates digests native DNA to nucleoside monophosphates. Complementation between recB21 and recC22 in vivo leads to normal levels of ATP-dependent nuclease activity. No complementation in vitro has been detected. Mutations in a third recombination gene (recA) do not alter significantly the wild-type levels of this nuclease activity.