Effect of DNA sequence and structure on nuclease activity of the DexA protein of bacteriophage T4

The bacteriophage T4 dexA gene product is required during infection of Escherichia coli strains carrying a mutation in the optA gene. We purified the DexA protein from cells which overproduced the protein. The protein was assayed for nuclease activity on synthetic di- and oligonucleotide substrates of known sequence and secondary structure. Sequence and structure significantly affected nuclease activity. The properties of the enzyme may explain the requirement for the DexA protein during infection of optA mutant hosts.