DNA-dependent RNA polymerases from Acanthamoeba castellanii. Comparative subunit structures of the homogeneous enzymes.
The constituent polypeptides of the three classes of DNA-dependent RNA polymerase from Acanthamoeba castellanii were compared by several electrophoretic methods. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS) reveals that a number of polypeptide components of the isozymes have identical molecular weights. Two-dimensional electrophoresis (isoelectric focusing in 8 M urea:SDS-polyacrylamide gel electrophoresis) demonstrates that the polypeptides of identical molecular weights also have identical isoelectric pH values. These polypeptides were also coincident after electrophoresis in 8 M urea at acidic or basic pH values followed by a second electrophoretic separation in the presence of SDS. By these criteria, subunits of molecular weight 13,300, 15,500, 17,500, 22,500, 37,000, and 39,000 are indistinguishable in polymerase I and III. The 13,300, 15,500, and 22,500 subunits are also shared by the class II polymerase. In addition, electrophoresis in 8 M urea under basic conditions reveals microheterogeneity in the 17,500 molecular weight subunit. The strikingly similar pattern of common subunits between yeast and Acanthamoeba suggests that a universal arrangement of functional units may be an essential feature of the eukaryotic polymerases.
D000656:Amoeba / Q000201:enzymology*; D000818:Animals; D012321:DNA-Directed RNA Polymerases / Q000302:isolation & purification; D004591:Electrophoresis, Polyacrylamide Gel; D007525:Isoelectric Focusing; D046911:Macromolecular Substances; D008970:Molecular Weight; D012318:RNA Polymerase I / Q000302:isolation & purification; D012319:RNA Polymerase II / Q000302:isolation & purification; D012320:RNA Polymerase III / Q000302:isolation & purification
D046911:Macromolecular Substances; D012319:RNA Polymerase II; D012321:DNA-Directed RNA Polymerases; D012318:RNA Polymerase I; D012320:RNA Polymerase III