1yhc

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Revision as of 04:39, 21 November 2007

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

Crystal structure of Aquifex aeolicus LpxC deacetylase complexed with cacodylate

Overview

UDP-3-O-((R)-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase (LpxC) is, a zinc-dependent enzyme that catalyzes the deacetylation of, UDP-3-O-((R)-3-hydroxymyristoyl)-N-acetylglucosamine to form, UDP-3-O-(R-hydroxymyristoyl)glucosamine and acetate. The structural, similarity of the active site of LpxC to metalloproteases led to the, proposal that LpxC functions via a metalloprotease-like mechanism. The pH, dependence of k(cat)/Km catalyzed by Escherichia coli and Aquifex aeolicus, LpxC displayed a bell-shaped curve (EcLpxC yields apparent pKa values of, 6.4+/-0.1 and 9.1+/-0.1), demonstrating that at least two ionizations are, important for maximal activity. Metal substitution and mutagenesis, experiments suggest that the basic limb of the pH profile is because of, deprotonation of a zinc-coordinated group such as the zinc-water molecule, whereas the acidic limb of the pH profile is caused by protonation of, either Glu78 or His265. Furthermore, the magnitude of the activity, decreases and synergy observed for the active site mutants suggest that, Glu78 and His265 act as a general acid-base catalyst pair. Crystal, structures of LpxC complexed with cacodylate or palmitate demonstrate that, both Glu78 and His265 hydrogen-bond with the same oxygen atom of the, tetrahedral intermediate and the product carboxylate. These structural, features suggest that LpxC catalyzes deacetylation by using Glu78 and, His265 as a general acid-base pair and the zinc-bound water as a, nucleophile.

About this Structure

1YHC is a Single protein structure of sequence from Aquifex aeolicus with ZN, CAC, SO4, CL, PAM and GOL as ligands. Full crystallographic information is available from OCA.

Reference

UDP-3-O-((R)-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase functions through a general acid-base catalyst pair mechanism., Hernick M, Gennadios HA, Whittington DA, Rusche KM, Christianson DW, Fierke CA, J Biol Chem. 2005 Apr 29;280(17):16969-78. Epub 2005 Feb 10. PMID:15705580

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