Targetting of protein phosphatase 1 to the sarcoplasmic reticulum of rabbit skeletal muscle by a protein that is very similar or identical to the G subunit that directs the enzyme to glycogen

Abstract

The amount of protein phosphatase 1 (PP1) activity in rabbit skeletal muscle associated with membranes (predominantly sarcoplasmic reticulum) is similar to that bound to glycogen‐protein particles. Membrane‐vesicleassociated (sarcovesicular) PP1 can be solubilised with 0.5% Triton X‐100 (but not 0.5 M NaCl) and is complexed to a protein that is structurally and functionally very similar or identical to the G subunit which targets PP1 to glycogen‐protein particles. This conclusion is based on immunoblotting and immunotitration experiments using two different preparations of G‐subunit‐specific antibodies, binding of Triton‐solubilised sarcovesicular enzyme to glycogen, stimulation of phosphory..