Purification and Characterization of RNA Polymerase from Fremyella diplosiphon

We have purified and characterized a DNA-dependent RNA polymerase from the blue-green alga Fremyella diplosiphon. This enzyme, purified by gel filtration, DEAE-cellulose chromatography, and glycerol gradient centrifugation, is comprised of five polypeptide subunits. Their masses are 161,000, 134,000, 91,000, 72,000, and 41,000 daltons. Preparative electrophoresis of the purified enzyme on nondenaturing gels separates the 41,000-dalton polypeptide from the rest of the enzyme. The enzyme is extremely labile in the presence of a variety of salts of strong acids and bases; the purification procedure was devised to avoid exposure to such compounds.