1m6v

From Proteopedia

---

Revision as of 19:04, 20 November 2007

proteopedia linkproteopedia link

spinqualitylabelsall models 1m6v, resolution 2.10Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal Structure of the G359F (small subunit) Point Mutant of Carbamoyl Phosphate Synthetase

Overview

Carbamoyl-phosphate synthetase catalyzes the production of carbamoyl, phosphate through a reaction mechanism requiring one molecule of, bicarbonate, two molecules of MgATP, and one molecule of glutamine. The, enzyme from Escherichia coli is composed of two polypeptide chains. The, smaller of these belongs to the Class I amidotransferase superfamily and, contains all of the necessary amino acid side chains required for the, hydrolysis of glutamine to glutamate and ammonia. Two homologous domains, from the larger subunit adopt conformations that are characteristic for, members of the ATP-grasp superfamily. Each of these ATP-grasp domains, contains an active site responsible for binding one molecule of MgATP., High resolution x-ray crystallographic analyses have shown that, remarkably, the three active sites in the E. coli enzyme are connected by, a molecular tunnel of approximately 100 A in total length. Here we, describe the high resolution x-ray crystallographic structure of the G359F, (small subunit) mutant protein of carbamoyl phosphate synthetase. This, residue was initially targeted for study because it resides within the, interior wall of the molecular tunnel leading from the active site of the, small subunit to the first active site of the large subunit. It was, anticipated that a mutation to the larger residue would "clog" the ammonia, tunnel and impede the delivery of ammonia from its site of production to, the site of utilization. In fact, the G359F substitution resulted in a, complete change in the conformation of the loop delineated by Glu-355 to, Ala-364, thereby providing an "escape" route for the ammonia intermediate, directly to the bulk solvent. The substitution also effected the, disposition of several key catalytic amino acid side chains in the small, subunit active site.

About this Structure

1M6V 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

Carbamoyl-phosphate synthetase. Creation of an escape route for ammonia., Thoden JB, Huang X, Raushel FM, Holden HM, J Biol Chem. 2002 Oct 18;277(42):39722-7. Epub 2002 Jul 18. PMID:12130656

Page seeded by OCA on Tue Nov 20 21:11:32 2007