1gim

From Proteopedia

Revision as of 14:08, 5 November 2007

CRYSTAL STRUCTURE OF ADENYLOSUCCINATE SYNTHETASE FROM ESCHERICHIA COLI COMPLEXED WITH GDP, IMP, HADACIDIN, NO3-, AND MG2+. DATA COLLECTED AT 100K (PH 6.5)

Overview

Crystal structures of adenylosuccinate synthetase from Esherichia coli, complexed with Mg2+, IMP, GDP, NO3- and hadacidin at 298 and 100 K have, been refined to R-factors of 0.188 and 0.206 against data to 2.8 A and 2.5, A resolution, respectively. Conformational changes of up to 9 A relative, to the unligated enzyme occur in loops that bind to Mg2+, GDP, IMP and, hadacidin. Mg2+ binds directly to GDP, NO3-, hadacidin and the protein, but is only five-coordinated. Asp13, which approaches, but does not occupy, the sixth coordination site of Mg2+, hydrogen bonds to N1 of IMP. The, nitrogen atom of NO3- is approximately 2.7 A from O6 of IMP, reflecting a, strong electrostatic interaction between the electron-deficient nitrogen, atom and the electron-rich O6. The spatial relationships between GDP, NO3-, and Mg2+ suggest an interaction between the beta,gamma-bridging oxygen, atom of GTP and Mg2+ in the enzyme-substrate complex. His41 hydrogen bonds, to the beta-phosphate group of GDP and approaches bound NO3-. The aldehyde, group of hadacidin coordinates to the Mg2+, while its carboxyl group, interacts with backbone amide groups 299 to 303 and the side-chain of, Arg303. The 5'-phosphate group of IMP interacts with Asn38, Thr129, Thr239, and Arg143 (from a monomer related by 2-fold symmetry). A mechanism is, proposed for the two-step reaction governed by the synthetase, in which, His41 and Asp13 are essential catalytic side-chains.

About this Structure

1GIM is a Single protein structure of sequence from Escherichia coli with MG, NO3, HAD, IMP and GDP as ligands. Active as Adenylosuccinate synthase, with EC number 6.3.4.4 Structure known Active Sites: ASP, GNS and IMP. Full crystallographic information is available from OCA.

Reference

Crystal structures of adenylosuccinate synthetase from Escherichia coli complexed with GDP, IMP hadacidin, NO3-, and Mg2+., Poland BW, Fromm HJ, Honzatko RB, J Mol Biol. 1996 Dec 20;264(5):1013-27. PMID:9000627

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