Full activation of a nuclear species of protein phosphatase-1 by phosphorylation with protein kinase A and casein kinase-2.
Bovine thymus nuclei contain a species of protein phosphatase-1 (PP-1N alpha) that can be partially activated by phosphorylation of an associated inhibitory polypeptide, NIPP-1, with protein kinase A [Beullens, Van Eynde, Bollen and Stalmans (1993) J. Biol. Chem. 268, 13172-13177]. Here it is shown that PP-1N alpha can also be activated 4-fold by phosphorylation of NIPP-1 with casein kinase-2. The effects of protein kinase A and casein kinase-2 were additive, yielding an enzyme with an activity close to that of the free catalytic subunit. Casein kinase-2 introduced up to 1.2 phosphate groups into purified NIPP-1 on serine and threonine residues. This phosphorylation was associated with a 14-fold increase in the concentration of NIPP-1 required for 50% inhibition of the type-1 catalytic subunit. The kinase-mediated inactivation of NIPP-1 could be reversed by incubation with the catalytic subunit of protein phosphatase-2A.
Van Eynde
A
A
Afdeling Biochemie, Fakulteit Geneeskunde, Katholieke Universiteit Leuven, Belgium.
Beullens
M
M
Stalmans
W
W
Bollen
M
M
D000818:Animals; D047388:Casein Kinases; D002417:Cattle; D002467:Cell Nucleus / Q000201:enzymology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D011817:Rabbits; D051381:Rats; D013552:Swine
D011494:Protein Kinases; D047388:Casein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2