The binding of 2-deoxy-D-glucose 6-phosphate to glycogen phosphorylase b: kinetic and crystallographic studies.Oikonomakos, N.G., Zographos, S.E., Johnson, L.N., Papageorgiou, A.C., Acharya, K.R.
(1995) J.Mol.Biol. 254: 900-917
- PubMed: 7500360
- DOI: 10.1006/jmbi.1995.0665
- PubMed Abstract:
- Crystallographic Binding Studies on the Allosteric Inhibitor Glucose-6- Phosphate to T State Glycogen Phosphorylase B
Johnson, L.N.,Snape, P.,Martin, J.L.,Acharya, K.R.,Barford, D.,Oikonomakos, N.G.
(1993) J.Mol.Biol. 232: 253
Kinetic and crystallographic studies have characterized the effect of 2-deoxy-glucose 6-phosphate on the catalytic and structural properties of glycogen phosphorylase b. Previous work on the binding of glucose 6-phosphate, a potent physiological inhi ...
Kinetic and crystallographic studies have characterized the effect of 2-deoxy-glucose 6-phosphate on the catalytic and structural properties of glycogen phosphorylase b. Previous work on the binding of glucose 6-phosphate, a potent physiological inhibitor of the enzyme, to T state phosphorylase b in the crystal showed that the inhibitor binds at the allosteric site and induces substantial conformational changes that affect the subunit-subunit interface. The hydrogen-bond from the O-2 hydroxyl of glucose 6-phosphate to the main-chain oxygen of Val40' represents the only hydrogen bond from the sugar to the other subunit, and this interaction appears important for promoting a more "tensed" structure than native T state phosphorylase b. 2-Deoxy-glucose 6-phosphate acts competitively with both the activator AMP and the substrate glucose 1-phosphate, with Ki values of 0.53 mM and 1.23 mM, respectively. The binding of 2-deoxy-glucose 6-phosphate to T state glycogen phosphorylase b in the crystal, has been investigated and the complex phosphorylase b: 2-deoxy-glucose 6-phosphate has been refined to give a crystallographic R factor of 17.3%, for data between 8 A and 2.3 A. 2-Deoxy-glucose 6-phosphate binds at the allosteric site as the a anomer and adopts a different conformation compared to glucose 6-phosphate. The two conformations differ by 160 degrees in the torsion angle about the C-5-C-6 bond. The contacts from the phosphate group are essentially identical to those made by the phosphate of glucose 6-phosphate but the 2-deoxy glucosyl moiety binds in a quite different orientation compared to the glucosyl of glucose 6-phosphate. 2-Deoxy-glucose 6-phosphate can be accommodated in the allosteric site with very little change in the protein, while structural comparisons show that the phosphorylase b: 2-deoxy-glucose 6-phosphate complex structure is overall more similar to a glucose-like complex than to the Glc-6-P complex structure.
Institute of Biological Research & Biotechnology, National Hellenic Research Foundation, Athens, Greece.