1s0y
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(New page: 200px<br /><applet load="1s0y" size="450" color="white" frame="true" align="right" spinBox="true" caption="1s0y, resolution 2.30Å" /> '''The structure of tra...)
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Revision as of 21:32, 24 November 2007
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The structure of trans-3-chloroacrylic acid dehalogenase, covalently inactivated by the mechanism-based inhibitor 3-bromopropiolate at 2.3 Angstrom resolution
Overview
Isomer-specific 3-chloroacrylic acid dehalogenases function in the, bacterial degradation of 1,3-dichloropropene, a compound used in, agriculture to kill plant-parasitic nematodes. The crystal structure of, the heterohexameric trans-3-chloroacrylic acid dehalogenase (CaaD) from, Pseudomonas pavonaceae 170 inactivated by 3-bromopropiolate shows that, Glu-52 in the alpha-subunit is positioned to function as the, water-activating base for the addition of a hydroxyl group to C-3 of, 3-chloroacrylate and 3-bromopropiolate, whereas the nearby Pro-1 in the, beta-subunit is positioned to provide a proton to C-2. Two arginine, residues, alphaArg-8 and alphaArg-11, interact with the C-1 carboxylate, groups, thereby polarizing the alpha,beta-unsaturated acids. The reaction, with 3-chloroacrylate results in the production of an unstable halohydrin, 3-chloro-3-hydroxypropanoate, which decomposes into the products malonate, semialdehyde and HCl. In the inactivation mechanism, however, malonyl, bromide is produced, which irreversibly alkylates the betaPro-1. CaaD is, related to 4-oxalocrotonate tautomerase, with which it shares an, N-terminal proline. However, in 4-oxalocrotonate tautomerase, Pro-1, functions as a base participating in proton transfer within a hydrophobic, active site, whereas in CaaD, the acidic proline is stabilized in a, hydrophilic active site. The altered active site environment of CaaD thus, facilitates a previously unknown reaction in the tautomerase superfamily, the hydration of the alpha,beta-unsaturated bonds of, trans-3-chloroacrylate and 3-bromopropiolate. The mechanism for these, hydration reactions represents a novel catalytic strategy that results in, carbon-halogen bond cleavage.
About this Structure
1S0Y is a Protein complex structure of sequences from Pseudomonas pavonaceae with MLA as ligand. Full crystallographic information is available from OCA.
Reference
The X-ray structure of trans-3-chloroacrylic acid dehalogenase reveals a novel hydration mechanism in the tautomerase superfamily., de Jong RM, Brugman W, Poelarends GJ, Whitman CP, Dijkstra BW, J Biol Chem. 2004 Mar 19;279(12):11546-52. Epub 2003 Dec 29. PMID:14701869
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