On the role of the dnaB protein of Escherichia coli in the replication of lambda bacteriophage DNA.

The interaction between the dnaB protein of E. coli and the gene P product of lambda bacteriophage was investigated by measuring the cleavage of closed circular phage DNA after infection of two temperature sensitive dnaB mutants, JG28 and To534 groP- B. Cleavage of superhelical DNA from a lambda pi B mutant phage was observed after infection of either strain whereas superhelical DNA from a wild type phage was only cleaved after infection of JG28. When DNA synthesis in infected cells was blocked by incubation at the nonpermissive temperature, no inhibition of superhelical phage DNA cleavage was observed. It is concluded that in conditions where the dnaB protein has lost the capacity to function in nucleotide polymerization, it is capable of interacting with the lambda replication gene products to introduce a break in the phage DNA.