spacer CRYSTAL STRUCTURE OF ADENYLOSUCCINATE SYNTHETASE FROM ESCHERICHIA COLI COMPLEXED WITH GDP, IMP, HADACIDIN, NO3-, AND MG2+. DATA COLLECTED AT 100K (PH 6.5)
Primary citation
Title Crystal structures of adenylosuccinate synthetase from Escherichia coli complexed with GDP, IMP hadacidin, NO3-, and Mg2+.
Authors Poland, B.W.search; Fromm, H.J.search; Honzatko, R.B.search
Journal J.MOL.BIOL.search vol:264, pag:1013-1027 (1996), Identifiers: PubMed ID (9000627)search DOI (10.1006/jmbi.1996.0693)
Abstract 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.
MeSH terms Adenylosuccinate Synthasesearch, Binding Sitessearch, Crystallographysearch, X-Raysearch, Electrochemistrysearch, Escherichia colisearch, Glycinesearch, Guanosine Diphosphatesearch, Inosine Monophosphatesearch, Magnesiumsearch, Modelssearch, Molecularsearch, Molecular Sequence Datasearch, Molecular Structuresearch, Nitratessearch, Protein Conformationsearch
Other entries described in this publication 1gin
Secondary citations
Title Refined Crystal Structures of Unligated Adenylosuccinate Synthetase from E.Coli
Authors Silva, M.M.search; Poland, B.W.search; Hoffman, C.R.search; Fromm, H.J.search; Honzatko, R.B.search
Journal J.MOL.BIOL.search vol:254, pag:431 (1995)
Title Crystal Structure of Adenylosuccinate Synthetase from E.Coli
Authors Poland, B.W.search; Silva, M.M.search; Serra, M.A.search; Cho, Y.search; Kim, K.H.search; Harris, E.M.search; Honzatko, R.B.search
Journal J.BIOL.CHEM.search vol:268, pag:25334 (1993)
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