Regulation of protein phosphatase‐1G from rabbit skeletal muscle: 2. Catalytic subunit translocation is a mechanism for reversible inhibition of activity toward glycogen‐bound substrates

Abstract

The glycogen‐associated form of protein phosphatase‐1 (PP‐1G) comprises a 37‐kDa catalytic (C) subunit and a 161‐kDa glycogen‐binding (G) subunit. In the preceding paper in this issue of the journal we showed that the C subunit is released from PP‐1G in response to phosphorylation of the G subunit by cAMP‐dependent protein kinase. We now show that at 0.15–02 M KCl the phosphorylase phosphatase activity of glycogen‐bound PP‐1G is 5–8 times higher than that of released C subunit or unbound PP‐1G, which are strongly inhibited at these ionic strengths. The activity of glycogen‐bound PP‐1G towards glycogen synthase was about 5‐fold higher than that of released C subunit at 0.15M KCl. Studies with..