1nht: Difference between revisions

Crystal structures of adenylosuccinate synthetase from Escherichia coli, complexed with Mg2+, 6-thiophosphoryl-IMP, GDP, and hadacidin at 298 and, 100 K have been refined to R-factors of 0.171 and 0.206 against data to, 2.8 and 2.5 A resolution, respectively. Interactions of GDP, Mg2+ and, hadacidin are similar to those observed for the same ligands in the, complex of IMP, GDP, NO3-, Mg2+ and hadacidin (Poland, B. W., Fromm, H. J., & Honzatko, R. B. (1996). J. Mol. Biol. 264, 1013-1027). Although crystals, were grown from solutions containing 6-mercapto-IMP and GTP, the electron, density at the active site is consistent with 6-thiophosphoryl-IMP and, GDP. Asp-13 and Gln-224 probably work in concert to stabilize the, 6-thioanion of 6-mercapto-IMP, which in turn is the nucleophile in the, displacement of GDP from the gamma-phosphate of GTP. Once formed, 6-thiophosphoryl-IMP is stable in the active site of the enzyme under the, conditions of the structural investigation. The direct observation of, 6-thiophosphoryl-IMP in the active site is consistent with the putative, generation of 6-phosphoryl-IMP along the reaction pathway of the, synthetase.

1NHT is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with MG, GDP, HAD and PGS as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Adenylosuccinate_synthase Adenylosuccinate synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=6.3.4.4 6.3.4.4] Structure known Active Sites: ASP, GNS and IMP. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1NHT OCA].  

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