A phosphorylation-initiated mechanism of local protein refolding activates yeast glycogen phosphorylase (GP). Refolding of the phosphorylated amino-terminus was shown to create a hydrophobic cluster that wedges into the subunit interface of the enzyme to trigger activation ...
A phosphorylation-initiated mechanism of local protein refolding activates yeast glycogen phosphorylase (GP). Refolding of the phosphorylated amino-terminus was shown to create a hydrophobic cluster that wedges into the subunit interface of the enzyme to trigger activation. The phosphorylated threonine is buried in the allosteric site. The mechanism implicates glucose 6-phosphate, the allosteric inhibitor, in facilitating dephosphorylation by dislodging the buried covalent phosphate through binding competition. Thus, protein phosphorylation-dephosphorylation may also be controlled through regulation of the accessibility of the phosphorylation site to kinases and phosphatases. In mammalian glycogen phosphorylase, phosphorylation occurs at a distinct locus. The corresponding allosteric site binds a ligand activator, adenosine monophosphate, which triggers activation by a mechanism analogous to that of phosphorylation in the yeast enzyme.
Related Citations:
Mechanism of Regulation in Yeast Glycogen Phosphorylase Lin, K., Hwang, P.K., Fletterick, R.J. (1995) J Biol Chem 270: 26833
Parallel Evolution in Two Homologues of Phosphorylase Rath, V.L., Fletterick, R.J. (1994) Nat Struct Biol 1: 681
Purification and Crystallization of Glycogen Phosphorylase from Saccharomyces Cerevisiae Rath, V.L., Hwang, P.K., Fletterick, R.J. (1992) J Mol Biol 225: 1027
Organizational Affiliation:
Department of Biochemistry and Biophysics, University of California at San Francisco, 513 Parnassus, San Francisco, CA 94143, USA.
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