Studies on In Vitro DNA Synthesis Isolation of dna B Gene Product from Escherichia coli

Formation of duplex DNA from varphiX174 single-stranded DNA by extracts of E. coli was previously shown to require the gene product of dna B. Using as an assay the stimulation of varphiX174 DNA-dependent synthesis in inactivated extracts of dna B temperature-sensitive cells, we purified the dna B gene product from wild-type E. coli as well as from a dna B temperature-sensitive mutant. The dna B temperature-sensitive gene product is more thermolabile than its wild-type counterpart.