On the Phosphorylation of Yeast RNA Polymerases A and B

Publisher Website
Google Scholar
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 favour of a modulation of RNA polymerase activity in vitro or in vivo via phosphorylation.