RNA polymerase from sporulating Bacillus subtilis. Purification and properties of a modified form of the enzyme containing two sporulation polypeptides.

A new form of DNA-dependent RNA polymerase termed enzyme III has been purified from sporulating cells of Bacillus subtilis. In addition to the subunits of core RNA polymerase (beta', beta, alpha, and omega), enzyme III contains sporulation-specific polypeptides of 85,000 (P85) and 27,000 (P27) daltons. P85 corresponds to an RNA polymerase-binding protein previously identified by precipitation of RNA polymerase from crude extracts of sporulating cells with antibody directed against core enzyme. Both P85 and P27 co-purified with RNA polymerase highly purified by gel filtration, DEAE-cellulose chromatography, phosphocellulose chromatography, and glycerol gradient centrifugation. Enzyme III bound more tightly to phosphocellulose and sedimented more rapidly during zone centrifugation than did RNA polymerase lacking the sporulation polypeptides. RNA polymerase containing P85 and P27 transcribed B. subtilis DNA about 4.5 times more actively than did core RNA polymerase, although both enzymes exhibited similar activities with poly(dA-dT) and phage phie DNA as templates. Enzyme III and core RNA polymerase also differed in their response to increasing concentrations of Mg2+ and KCl.