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.