Module 5: Figure PP1 targeting to glycogen
Function of the regulatory proteins GM and GL in targeting protein phosphatase 1 (PP1) to both glycogen and the sarcoplasmic reticulum.
The regulatory protein GM in skeletal muscle or GL in liver has two targeting domains. One is located in the middle of the molecule (shown in green) that directs protein phosphatase 1 (PP1) to glycogen, where it can dephosphorylate the enzymes glycogen synthase and phosphorylase that control glycogen synthesis and glycogenolysis respectively. The other is a transmembrane region (shown in blue) in the C-terminal region that directs PP1 towards the sarcoplasmic reticulum, where it acts to dephosphorylate phospholamban, which functions to regulate the activity of the sarco/endo-plasmic reticulum Ca2+-ATPase 2 (SERCA2a) pump (Module 5: Figure phospholamban mode of action).