Role of the modulator protein in the interconversion of rabbit skeletal muscle protein phosphatase.
The major active protein phosphatase present in a rabbit skeletal muscle extract is associated with the glycogen particle and migrates in sucrose density gradient centrifugation as a Mr = 70,000 protein and contains modulator activity. Addition of extra modulator protein causes a time- and concentration-dependent conversion of the enzyme to an inactive FA-ATP, Mg-dependent form. The intrinsic modulator in the active phosphatase is destroyed by limited proteolysis without an appreciable change in the phosphatase activity. The proteolyzed active enzyme has a lower molecular weight (Mr = 40,000) and it reassociates with the modulator producing a FA-ATP, Mg-dependent enzyme form (Mr = 60,000). The modulator protein is used stoichiometrically in the activation of the ATP, Mg-dependent phosphatase. This is in agreement with the presence of one unit of modulator activity per unit of native spontaneously active phosphatase.
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D004789:Enzyme Activation; D007700:Kinetics; D008970:Molecular Weight; D009132:Muscles / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000302:isolation & purification / Q000378:metabolism*; D011506:Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011817:Rabbits
D011506:Proteins; C488948:deinhibitor protein, Oryctolagus cuniculus; D000255:Adenosine Triphosphate; D010749:Phosphoprotein Phosphatases