Immunochemical characterization of the modulator protein of the ATP,Mg-dependent protein phosphatase.

Polyclonal antibodies raised against the modulator protein of the ATP,Mg-dependent protein phosphatase completely neutralize all known properties of the purified modulator: inhibition or inactivation of the phosphatase catalytic subunit as well as the kinase FA-mediated activation of the ATP,Mg-dependent phosphatase. They do not cross-react with phosphoinhibitor-1 or the phosphatase catalytic subunit. Direct analysis of boiled or unboiled skeletal muscle extracts by Western blotting reveals a 32 kDa polypeptide corresponding to the modulator protein as the most dominant protein staining band.