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

Abstract

Abstract The nuclear DNA-dependent RNA polymerases have been partially purified from the slime mold Physarum polycephalum. Two major forms of the enzyme are readily separated upon phosphocellulose chromatography. One of these (R) is resistant to the mushroom toxin α-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 α-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: 200,0001; 135,0001; 45,0001; 24,0002; 17,0001.