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.