Amino acid sequence and expression of the hepatic glycogen-binding (GL-subunit of protein phosphatase-1

AbstractA full-length cDNA encoding the putative hepatic glycogen-binding (GL) subunit of protein phosphatase-1 (PP1) 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 (GM) subunit of PP1 from striated muscle. The similarities between GM and GL were most striking between residues 63–86, 144–166 and 186–227 of human GM (∼40% identity), nearly all the identities with the putative yeast homologue GAC1 being located between 144–166 and 186–227. The cDNA was expressed in E. coli, and the expressed protein transformed the properties of PP1 to those characteristic of the hepatic glycogen-associated enzyme. These experiments establish that the cloned protein is GL