title: On the phosphorylation of yeast RNA polymerases A and B.
abstract: In exponentially growing cells, RNA polymerase B is exclusively form BI enzyme with several phosphorylated subunits: B220, B23 and possibly B44.5. In RNA polymerase A an average of fifteen phosphate groups are distributed on the five phosphorylated subunits: A190 (6), A43 (4), A34.5 (2), A23 (1-2) and A19 (1-2). Phosphorylation of enzyme A by a yeast protein kinase in vitro adds less than 1 mol phosphate/mol enzyme but occurs essentially at the physiological sites, as shown by a comparison of the peptide patterns obtained by limited proteolysis of subunits 32P-labelled in vivo and in vitro. No evidence was found in favor of a modulation of RNA polymerase activity in vitro or in vivo via phosphorylation.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D007700:Kinetics; D010766:Phosphorylation; D012318:RNA Polymerase I / Q000378:metabolism*; D012319:RNA Polymerase II / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*
chemical_list: D012319:RNA Polymerase II; D012321:DNA-Directed RNA Polymerases; D012318:RNA Polymerase I