Deoxyribonucleic acid-dependent ribonucleic acid polymerases in the dimorphic fungus Mucor rouxii

Three forms of DNA-dependent RNA polymerase have been separated by chromatography of extracts of yeast-like cells and mycelium of the dimorphic fungus Mucor rouxii. Each of the three eznymes has been purified by means of protamine sulfate precipitation, ion exchange chromatography, affinity chromatography, and velocity sedimentation. Electrophoresis under denaturing conditions showed differences in the subunit compositions of all three purified enzymes. The properties of the enzymes from M. rouxii were similar to those of polymerases from other eukaryotic organisms. Denatured DNA was a better template than native DNA for all three enzymes but each enzyme had a distinct pattern of activities with different templates. Enzymes I and III displayed optimal activity with Mn-2gs the divalent cation and were stimulated significantly by Kcl and (NH4)2S04. Enzyme II had a greater activity with Mg-2gnd was only slightly stimulated by KCl and (NH4)2SO4. None of the enzymes were inhibited by cycloheximide or by rifampicin: all were inhibited by actinomycin C and rifampin AF/018: only enzyme II was inhibited by alpha-amanitin. No differences could be found in the properties of the same enzymes isolated from yeast-like cells or mycelium.