1z62

From Proteopedia

Revision as of 05:08, 21 November 2007

Indirubin-3'-aminooxy-acetate inhibits glycogen phosphorylase by binding at the inhibitor and the allosteric site. Broad specificities of the two sites

Overview

The binding of indirubin-5-sulphonate (E226), a potential anti-tumour, agent and a potent inhibitor (IC(50) = 35 nm) of cyclin-dependent kinase 2, (CDK2) and glycogen phosphorylase (GP) has been studied by kinetic and, crystallographic methods. Kinetic analysis revealed that E226 is a, moderate inhibitor of GPb (K(i) = 13.8 +/- 0.2 micro m) and GPa (K(i) =, 57.8 +/- 7.1 micro m) and acts synergistically with glucose. To explore, the molecular basis of E226 binding we have determined the crystal, structure of the GPb/E226 complex at 2.3 A resolution. Structure analysis, shows clearly that E226 binds at the purine inhibitor site, where caffeine, and flavopiridol also bind [Oikonomakos, N.G., Schnier, J.B., Zographos, S.E., Skamnaki, V.T., Tsitsanou, K.E. & Johnson, L.N. (2000) J. Biol., Chem.275, 34566-34573], by intercalating between the two aromatic rings of, Phe285 and Tyr613. The mode of binding of E226 to GPb is similar, but not, identical, to that of caffeine and flavopiridol. Comparative structural, analyses of the GPb-E226, GPb-caffeine and GPb-flavopiridol complex, structures reveal the structural basis of the differences in the potencies, of the three inhibitors and indicate binding residues in the inhibitor, site that can be exploited to obtain more potent inhibitors. Structural, comparison of the GPb-E226 complex structure with the active pCDK2-cyclin, A-E226 complex structure clearly shows the different binding modes of the, ligand to GPb and CDK2; the more extensive interactions of E226 with the, active site of CDK2 may explain its higher affinity towards the latter, enzyme.

About this Structure

1Z62 is a Single protein structure of sequence from Oryctolagus cuniculus with PLP and IAA as ligands. Active as Phosphorylase, with EC number 2.4.1.1 Full crystallographic information is available from OCA.

Reference

Binding of the potential antitumour agent indirubin-5-sulphonate at the inhibitor site of rabbit muscle glycogen phosphorylase b. Comparison with ligand binding to pCDK2-cyclin A complex., Kosmopoulou MN, Leonidas DD, Chrysina ED, Bischler N, Eisenbrand G, Sakarellos CE, Pauptit R, Oikonomakos NG, Eur J Biochem. 2004 Jun;271(11):2280-90. PMID:15153119

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