title: Dissociation of two polypeptide chains from yeast RNA polymerase A.
abstract: Yeast RNA polymerase A (RNA nucleotidyltransferase; nucleosidetriphosphate:RNA nucleotidyltransferase; EC 2.7.7.6) can be converted to a new form of enzyme, called RNA polymerase A*, which is lacking two polypeptide chains of 48,000 and 37,000 daltons. Apart from these two missing polypeptides the subunit structures of RNA polymerases A and A* are indistinguishable. RNA polymerase A* differs from the complete enzyme in its electrophoretic and chromatographic behavior, template requirements, and alpha-amanitin sensitivity. RNA polymerase A* transcribes the alternated copolymer d(A-T)n with the same efficiency as RNA polymerase A but its specific activity is greatly reduced with native calf thymus DNA as template. The transcription of a variety of synthetic templates is also altered by removal of the two polypeptide chains. RNA polymerase A* is inhibited by high concentrations of alpha-amanitin (500 mug/ml), whereas RNA polymerase A is comparatively less sensitive to the toxic peptide. The data are discussed in terms of possible roles of the two dissociable polypeptides.
mesh_terms: D000546:Amanitins / Q000494:pharmacology; D012321:DNA-Directed RNA Polymerases / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D046911:Macromolecular Substances; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D008970:Molecular Weight; D010455:Peptides / Q000032:analysis; D011233:Precipitin Tests; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013698:Templates, Genetic
chemical_list: D000546:Amanitins; D046911:Macromolecular Substances; D010455:Peptides; D008345:Manganese; D012321:DNA-Directed RNA Polymerases; D008274:Magnesium