1kee: Difference between revisions

[[Image:1kee.jpg|left|200px]]<br /><applet load="1kee" size="350" color="white" frame="true" align="right" spinBox="true"  

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.

1KEE is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=MN:'>MN</scene>, <scene name='pdbligand=K:'>K</scene>, <scene name='pdbligand=CL:'>CL</scene>, <scene name='pdbligand=PO4:'>PO4</scene>, <scene name='pdbligand=ADP:'>ADP</scene>, <scene name='pdbligand=ORN:'>ORN</scene> and <scene name='pdbligand=NET:'>NET</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Carbamoyl-phosphate_synthase_(glutamine-hydrolyzing) Carbamoyl-phosphate synthase (glutamine-hydrolyzing)], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=6.3.5.5 6.3.5.5] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1KEE OCA].  

[[Category: Holden, H M.]]

[[Category: Miles, B W.]]

[[Category: Raushel, F M.]]

[[Category: Thoden, J B.]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:33:10 2008''