PMID:11729189

Citation	Miles, BW, Thoden, JB, Holden, HM and Raushel, FM (2002) Inactivation of the amidotransferase activity of carbamoyl phosphate synthetase by the antibiotic acivicin. J. Biol. Chem. 277:4368-73
Abstract	Carbamoyl phosphate synthetase (CPS) from Escherichia coli catalyzes the formation of carbamoyl phosphate from 2 mol of ATP, bicarbonate, and glutamine. CPS was inactivated by the glutamine analog, acivicin. In the presence of ATP and bicarbonate the second-order rate constant for the inactivation of the glutamine-dependent activities was 4.0 x 10(4) m(-1) s(-1). In the absence of ATP and bicarbonate the second-order rate constant for inactivation of CPS was reduced by a factor of 200. The enzyme was protected against inactivation by the inclusion of glutamine in the reaction mixture. The ammonia-dependent activities were unaffected by the incubation of CPS with acivicin. These results are consistent with the covalent labeling of the glutamine-binding site located within the small amidotransferase subunit. The binding of ATP and bicarbonate to the large subunit of CPS must also induce a conformational change within the amidotransferase domain of the small subunit that enhances the nucleophilic character of the thiol group required for glutamine hydrolysis. The acivicin-inhibited enzyme was crystallized, and the three-dimensional structure was determined by x-ray diffraction techniques. The thiol group of Cys-269 was covalently attached to the dihydroisoxazole ring of acivicin with the displacement of a chloride ion.
Links	PubMed Online version:10.1074/jbc.M108582200
Keywords	Anthranilate Synthase; Anti-Bacterial Agents/pharmacology; Carbamoyl-Phosphate Synthase (Ammonia)/antagonists & inhibitors; Carbamoyl-Phosphate Synthase (Ammonia)/chemistry; Carbamoyl-Phosphate Synthase (Ammonia)/metabolism; Crystallography, X-Ray; Enzyme Inhibitors/pharmacology; Escherichia coli/enzymology; Isoxazoles/pharmacology; Kinetics; Models, Molecular; Nitrogenous Group Transferases/antagonists & inhibitors; Nitrogenous Group Transferases/chemistry; Nitrogenous Group Transferases/metabolism; Protein Conformation
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