Purification of mitochondrial RNA polymerase from Saccharomyces cerevisiae.

The RNA polymerase from the mitochondria of Saccharomyces cerevisiae has been extensively purified by Sepharose 4B, heparin Sepharose 4B phosphocellulose, and DEAE-Sephadex A-50 chromatography. The activity co-sediments with a 45,000-dalton polypeptide at 6.3 S in glycerol gradients. The activity is inhibited by antibodies to the 45,000-dalton polypeptide. The activity is not inhibited by rifampicin or alpha-amanitin. It requires Mg2+ and is inhibited by elevated ionic strength and Mn2+. The most efficient template for the RNA polymerase is poly[d(AT)], with mtDNA being the preferred natural template. The RNA polymerase transcribes mtDNA from the petite strain F11 in a nonrandom manner.