1kkf
Complex of E. coli Adenylosuccinate Synthetase with IMP, Hadacidin, Pyrophosphate, and Mg
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OverviewOverview
A complete set of substrate/substrate analogs of adenylosuccinate, synthetase from Escherichia coli induces dimer formation and a transition, from a disordered to an ordered active site. The most striking of the, ligand-induced effects is the movement of loop 40-53 by up to 9 A. Crystal, structures of the partially ligated synthetase, which either combine IMP, and hadacidin or IMP, hadacidin, and Mg(2+)-pyrophosphate, have ordered, active sites, comparable with the fully ligated enzyme. More, significantly, a crystal structure of the synthetase with IMP alone, exhibits a largely ordered active site, which includes the 9 A movement of, loop 40-53 but does not include conformational adjustments to backbone, carbonyl 40 (Mg(2+) interaction element) and loop 298-304 (L-aspartate, binding element). Interactions involving the 5'-phosphoryl group of IMP, evidently trigger the formation of salt links some 30 A away. The above, provides a structural basis for ligand binding synergism, effects on, k(cat) due to mutations far from the site of catalysis, and the complete, loss of substrate efficacy due to minor alterations of the 5'-phosphoryl, group of IMP.
About this StructureAbout this Structure
1KKF is a Single protein structure of sequence from Escherichia coli with MG, DPO, HAD and IMP as ligands. Active as Adenylosuccinate synthase, with EC number 6.3.4.4 Full crystallographic information is available from OCA.
ReferenceReference
IMP Alone Organizes the Active Site of Adenylosuccinate Synthetase from Escherichia coli., Hou Z, Wang W, Fromm HJ, Honzatko RB, J Biol Chem. 2002 Feb 22;277(8):5970-6. Epub 2001 Dec 12. PMID:11741996
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