Yeast protein phosphatase active with acidic ribosomal proteins

A protein phosphatase dephosphorylating acidic ribosomal proteins was purified from Saccharomyces cerevisiae ribosome-free extract. It was shown that phosphoproteins from both P1 and P2 subfamilies as well as 60S "core" P0 protein were substrates for the enzyme. The phosphatase can dephosphorylate ribosomes as well as histones and casein but the two last substrates with significantly lower efficiency. It was found that the enzyme activity is Mn(2+)-dependent and inhibited by okadaic acid, tautomycin, cantharidin and nodularin at concentrations typical for protein phosphatase type 2A. The possible implications of those findings in the control of ribosome phosphorylation and therefore in the control of translation is discussed.