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PP1C binding domain found in protein phosphatase 1 regulatory subunit 3 (PPP1R3) family The PPP1R3 family includes three protein phosphatase 1 regulatory subunits, PPP1R3A, PPP1R3B and PPP1R3C, that act as glycogen-targeting subunits for protein phosphatase 1 (PP1). PPP1R3A, also called protein phosphatase 1 glycogen-associated regulatory subunit (PP1G), protein phosphatase type-1 glycogen targeting subunit, or RG1, is essential for cell division, and participates in the regulation of glycogen metabolism, muscle contractility, and protein synthesis. PPP1R3A plays an important role in glycogen synthesis but is not essential for insulin activation of glycogen synthase. PPP1R3B, also called hepatic glycogen-targeting protein phosphatase 1 regulatory subunit GL, protein phosphatase 1 regulatory subunit 4, PP1 subunit R4, or protein phosphatase 1 subunit GL, facilitates interaction of the PP1 with enzymes of the glycogen metabolism and regulates its activity. PPP1R3B suppresses the rate at which PP1 dephosphorylates (inactivates) glycogen phosphorylase and enhances the rate at which it activates glycogen synthase and therefore limits glycogen breakdown. Its activity is inhibited by glycogen phosphorylase liver form (PYGL), resulting in inhibition of the glycogen synthase and glycogen phosphorylase phosphatase activities of PP1. PPP1R3C, also called protein phosphatase 1 regulatory subunit 5 (PPP1R5), PP1 subunit R5, or protein targeting to glycogen (PTG), activates glycogen synthase, reduces glycogen phosphorylase activity and limits glycogen breakdown. It can dramatically increase basal and insulin-stimulated glycogen synthesis upon overexpression in a variety of cell types. This model corresponds to protein phosphatase 1 catalytic subunit (PP1C) binding domain, which contains a RVxF PP1C-binding motif that mediates interactions with PP1C. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",