The primary structure of rat liver glycogen synthase deduced by cDNA cloning. Absence of phosphorylation sites 1a and 1b.
The cDNA for rat liver glycogen synthase was isolated by screening a rat liver cDNA library constructed in lambda gt11. The cDNA was 2.4 kilobases in length and encoded a protein of 703 amino acid residues with a molecular mass of 80.5 kDa. Comparison of the rat liver and the human muscle sequences show that the amino- and carboxyl-terminal regions are quite divergent as compared to the internal sequences which show an 80% identity. The rat liver carboxyl-terminal region is truncated by 33 residues and has only 46% identity with the muscle sequence but retains the common feature of a low content of hydrophobic amino acids (13%). Phosphorylation sites 1a and 1b, which are the primary targets for phosphorylation by cAMP-dependent protein kinase, are absent in the liver sequence. The presence of these divergent, structurally anomalous carboxyl-terminal regions in liver and muscle glycogen synthase suggests the absence of the requirement that they possess a tertiary structure that is integral to that of the protein core. A model is proposed in which this region interacts with a catalytic core to maintain the I state, and in which phosphorylation serves to uncouple this interaction.
Bai
G
G
Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, Florida 33101.
Zhang
Z J
ZJ
Werner
R
R
Nuttall
F Q
FQ
Tan
A W
AW
Lee
E Y
EY
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics*; D015246:Deoxyribonuclease EcoRI; D006006:Glycogen Synthase / Q000235:genetics*; D006801:Humans; D008099:Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009132:Muscles / Q000201:enzymology; D010766:Phosphorylation; D014176:Protein Biosynthesis; D011817:Rabbits; D051381:Rats; D012045:Regulatory Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid
D004247:DNA; D006006:Glycogen Synthase; D015246:Deoxyribonuclease EcoRI