2prj
From Proteopedia
Binding of N-acetyl-beta-D-glucopyranosylamine to Glycogen Phosphorylase B
Structural highlights
FunctionPYGM_RABIT Phosphorylase is an important allosteric enzyme in carbohydrate metabolism. Enzymes from different sources differ in their regulatory mechanisms and in their natural substrates. However, all known phosphorylases share catalytic and structural properties. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedStructure-based drug design has led to the discovery of a number of glucose analogue inhibitors of glycogen phosphorylase that have an increased affinity compared to alpha-D-glucose (Ki = 1.7 mM). The best inhibitor in the class of N-acyl derivatives of beta-D-glucopyranosylamine, N-acetyl-beta-D-glucopyranosylamine (1-GlcNAc), has been characterized by kinetic, ultracentrifugation, and crystallographic studies. 1-GlcNAc acts as a competitive inhibitor for both the b (Ki = 32 microM) and the a (Ki = 35 microM) forms of the enzyme with respect to glucose 1-phosphate and in synergism with caffeine, mimicking the binding of glucose. Sedimentation velocity experiments demonstrated that 1-GlcNAc was able to induce dissociation of tetrameric phosphorylase a and stabilization of the dimeric T-state conformation. Co-crystals of the phosphorylase b-1-GlcNAc-IMP complex were grown in space group P4(3)2(1)2, with native-like unit cell dimensions, and the complex structure has been refined to give a crystallographic R factor of 18.1%, for data between 8 and 2.3 A resolution. 1-GlcNAc binds tightly at the catalytic site of T-state phosphorylase b at approximately the same position as that of alpha-D-glucose. The ligand can be accommodated in the catalytic site with very little change in the protein structure and stabilizes the T-state conformation of the 280s loop by making several favorable contacts to Asn 284 of this loop. Structural comparisons show that the T-state phosphorylase b-1-GlcNAc-IMP complex structure is overall similar to the T-state phosphorylase b-alpha-D-glucose complex structure. The structure of the 1-GlcNAc complex provides a rational for the biochemical properties of the inhibitor. N-acetyl-beta-D-glucopyranosylamine: a potent T-state inhibitor of glycogen phosphorylase. A comparison with alpha-D-glucose.,Oikonomakos NG, Kontou M, Zographos SE, Watson KA, Johnson LN, Bichard CJ, Fleet GW, Acharya KR Protein Sci. 1995 Dec;4(12):2469-77. PMID:8580837[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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