A DNA-dependent ATPase from T4-infected Escherichia coli. Purification and properties of a 63,000-dalton enzyme and its conversion to a 22,000-dalton form.

A DNA-dependent ATPase with a molecular weight of 63,000 has been purified to near homogeneity from T4-infected Escherichia coli. This enzyme is not present in uninfected E. coli. It is present in E. coli infected with amber mutants of gene 44 or gene 62 and with the data mutant. The enzyme can be eluted from single-stranded DNA-cellulose at NaCl molarities greater than 0.6 M and from ATP agarose with 80 mM MgATP. The enzyme hydrolyzes MgATP or MgdATP to the diphosphates with equal maximum velocities and the Km values are 0.30 and 0.75 mM, respectively. The enzyme hydrolyzes MgCTP with 13% and MgUTP with 7% of the velocity observed with MgATP. Apparent Km values are reported for single-stranded T4 DNA and for a series of synthetic polynucleotides. The 63,000-dalton enzyme can be cleaved proteolytically to an active 22,000-dalton form. This can be demonstrated by storage of infected cells, by mixing of cell extracts, and by inhibition with phenylmethylsulfonyl fluoride. The Mr = 22,000 enzyme cross-reacts with antibody made to the Mr = 63,000 enzyme. This antibody inhibits the 22,000-dalton species. The 22,000-dalton enzyme forms a complex with gene 32 protein in the absence of DNA.