1kee

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spinqualitylabelsall models 1kee, resolution 2.10Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Inactivation of the Amidotransferase Activity of Carbamoyl Phosphate Synthetase by the Antibiotic Acivicin

Overview

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.

About this Structure

1KEE is a Protein complex structure of sequences from Escherichia coli with MN, K, CL, PO4, ADP, ORN and NET as ligands. Active as Carbamoyl-phosphate synthase (glutamine-hydrolyzing), with EC number 6.3.5.5 Full crystallographic information is available from OCA.

Reference

Inactivation of the amidotransferase activity of carbamoyl phosphate synthetase by the antibiotic acivicin., Miles BW, Thoden JB, Holden HM, Raushel FM, J Biol Chem. 2002 Feb 8;277(6):4368-73. Epub 2001 Nov 29. PMID:11729189

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