Phosphorylation of the catalytic subunit of type-1 protein phosphatase by the v-abl tyrosine kinase.
The catalytic subunit of type-1 protein phosphatase (PP1) was phosphorylated by the tyrosine kinase v-abl as follows: (i) cytosolic PP1 was phosphorylated more (0.73 mol/mol) than PP1 obtained from the glycogen particles (0.076 mol/mol), while free catalytic subunit isolated in the active or inactive form from cytosolic PP1 was phosphorylated even less and catalytic subunit complexed with inhibitor-2 was not phosphorylated; (ii) phosphorylation stoichiometry was dependent on the concentration of PP1 and 3 h incubation at 30 degrees C was required for maximal phosphorylation; (iii) phosphorylation was on a tyrosine residue located in the C-terminal region of PP1 which is lost during proteolysis; (iv) phosphorylation did not affect enzyme activity but allowed conversion from the active to the inactive form upon incubation with inhibitor-2 of a PP1 form that in its dephospho-form did not convert.
Villa-Moruzzi
E
E
Department of Biomedicine, University of Pisa, Italy.
Dalla Zonca
P
P
Crabb
J W
JW
D000818:Animals; D002384:Catalysis; D004789:Enzyme Activation; D016374:Oncogene Proteins v-abl / Q000378:metabolism* / Q000502:physiology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism* / Q000502:physiology; D011817:Rabbits; D011994:Recombinant Proteins / Q000502:physiology; D013379:Substrate Specificity
D016374:Oncogene Proteins v-abl; D011994:Recombinant Proteins; D011505:Protein-Tyrosine Kinases; D010749:Phosphoprotein Phosphatases