Amino acid sequence and expression of the hepatic glycogen‐binding (G_L‐subunit of protein phosphatase‐1

Abstract

A full-length cDNA encoding the putative hepatic glycogen-binding (G,) subunit of protein phosphatase-1 (PPl) was isolated from a rat liver library. The deduced amino acid sequence (284 residues, 32.6 kDa) was 23% identical (39% similar) to the N-terminal region of the glycogen-binding (G,) subunit of PPl from striated muscle. The similarities between GM and G, were most striking between residues 63-f&& 16166 and 186-227 of human G, (-40% identity), nearly all the identities with the putative yeast homologue GACl being located between 144-166 and 186-227. The cDNA was expressed in E. coli, and the expressed protein transformed the properties of PPl to those characteristic of the hepatic glycogen-associated enzyme. These experiments establish that the cloned protein is G,.

Characterization of the interaction between DARPP-32 and protein phosphatase 1 (PP-1): DARPP-32 peptides antagonize the interaction of PP-1 with binding proteins

“…The structure of the enzyme has revealed multiple surface grooves emanating from the active site (28). Site-directed mutagenesis studies suggest that amino acids surrounding the phosphorylation site of phosphorylase a might possibly occupy the COOH-terminal groove of PP-1C (30,40). Thus, certain targeting proteins may occupy the phosphorylase a binding site while leaving alternative binding modes available in which other PP-1C surface grooves could accommodate specific substrates brought into immediate proximity by binding to the targeting proteins.…”

Biophysical interaction between phospholamban and protein phosphatase 1 regulatory subunit GM

“…Amongst them, GL targets PP1C to liver glycogen [18,19], M110 is responsible for the association of PP1 with the myo¢brils of skeletal muscle [20,21] and spinophilin is a novel PP1 binding protein identi¢ed recently in dendritic spines [22]. In fact, at least 15 regulatory subunits able to interact with the same catalytic subunit PP1C have been identi¢ed to date in mammals [11], allowing PP1 to regulate diverse functions.…”

A Protein Phosphatase-1-binding Motif Identified by the Panning of a Random Peptide Display Library

“…On the other hand, two other peptides containing the VHW motif were not inhibitory. The differential effects on the inhibition of phosphorylase phosphatase activity observed with the peptides are not surprising, given that the binding of the G M subunit has been shown to partially inhibit phosphorylase phosphatase activity, but to increase activity toward glycogen synthase (15,22,34). It remains a possibility that binding of variants of the PP1-binding motif could produce differential effects on either activity or substrate specificity.…”

“…These include genes that are variously required for control of glycogen metabolism, glucose repression, meiosis and/or sporulation, and mitotic cell cycle regulation (19 -21). Thus, PP1 is unusual in that this single enzyme is involved in the regulation of a number of diverse cellular processes.Few, if any, of the PP1 proteins share any major sequence identity, although examination of different glycogen-binding subunits has revealed the presence of two small regions of sequence similarity that is shared between several glycogenbinding proteins (20,(22)(23)(24)(25). The unusually large number of PP1-binding proteins that have been described suggests either that PP1 contains a motif that is recognized by a common binding structure on this diverse group of proteins or that the latter contain a protein motif that is recognized by a single binding site on PP1.…”