Purification and Properties of Deoxyribonucleic Acid-dependent Ribonucleic Acid Polymerases from the Slime Mold Physarum polycephalum

The nuclear DNA-dependent RNA polymerases have been partially purified from the slime mold Physarum polycepha-Zum.Two major forms of the enzyme are readily separated upon phosphocellulose chromatography.One of these (R) is resistant to the mushroom toxin cY-amanitin, has a low salt optimum, and has a relatively low preference for denatured DNA over native DNA.This enzyme is therefore probably identifiable with RNA polymerase I from the higher eukaryotes.The other enzyme (S) is sensitive to cr-amanitin, has a relatively high salt optimum, and has a relatively high preference for denatured DNA over native DNA.This enzyme is apparently analogous to RNA polymerase II from the higher eukaryotes.Slime mold RNA polymerase R has been purified to near homogeneity.This enzyme has a sedimentation coefficient of approximately 13.1 S. Polyacrylamide gels run under denaturing conditions reveal a probable subunit structure as follows: 200,