A novel adenosine triphosphatase isolated from RNA polymerase preparations of Escherichia coli. II. Enzymatic properties and molecular structure.

An adenosinetriphosphatase (ATPase) [EC 3.6.1.3] copurified with the DNA-dependent RNA polymerase [EC 2.7.7.6] from Escherichia coli was isolated to apparent homogeneity and some of its functional as well as structural properties were examined. Although the novel ATPase exhibited metal requirements similar to those of Mg2+, Ca2+-ATPase, its response to NaN3 and antisera appeared completely different from that of the Mg2+, Ca2+-ATPase. The purified ATPase was found to be a large protein with a molecular weight of 9.3X10(5) daltons, composed of identical subunits of 7X10(4) daltons. When viewed under an electron microscope, the ATPase appeared to be very similar to material previously misidentified as the RNA polymerase. The physiological role of the novel ATPase, however, remains unclear.