Send to

Choose Destination
See comment in PubMed Commons below
J Biol Chem. 1997 Jun 13;272(24):15200-5.

Entrapment of 6-thiophosphoryl-IMP in the active site of crystalline adenylosuccinate synthetase from Escherichia coli.

Author information

  • 1Department of Biochemistry and Biophysics, Iowa State University, Ames, Iowa 50011, USA.


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.

[PubMed - indexed for MEDLINE]
Free full text

LinkOut - more resources

Full Text Sources

Other Literature Sources

Molecular Biology Databases

PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire
    Loading ...
    Support Center