2flt
From Proteopedia
|
The X-ray structure of the cis-3-chloroacrylic acid dehalogenase cis-CaaD inactivated with (R)-Oxirane-2-carboxylate
Overview
The bacterial degradation pathways for the nematocide 1,3-dichloropropene, rely on hydrolytic dehalogenation reactions catalyzed by cis- and, trans-3-chloroacrylic acid dehalogenases (cis-CaaD and CaaD, respectively). X-ray crystal structures of native cis-CaaD and cis-CaaD, inactivated by (R)-oxirane-2-carboxylate were elucidated. They locate four, known catalytic residues (Pro-1, Arg-70, Arg-73, and Glu-114) and two, previously unknown, potential catalytic residues (His-28 and Tyr-103')., The Y103F and H28A mutants of these latter two residues displayed, reductions in cis-CaaD activity confirming their importance in catalysis., The structure of the inactivated enzyme shows covalent modification of the, Pro-1 nitrogen atom by (R)-2-hydroxypropanoate at the C3 position. The, interactions in the complex implicate Arg-70 or a water molecule bound to, Arg-70 as the proton donor for the epoxide ring-opening reaction and, Arg-73 and His-28 as primary binding contacts for the carboxylate group., This proposed binding mode places the (R)-enantiomer, but not the, (S)-enantiomer, in position to covalently modify Pro-1. The absence of, His-28 (or an equivalent) in CaaD could account for the fact that CaaD is, not inactivated by either enantiomer. The cis-CaaD structures support a, mechanism in which Glu-114 and Tyr-103' activate a water molecule for, addition to C3 of the substrate and His-28, Arg-70, and Arg-73 interact, with the C1 carboxylate group to assist in substrate binding and, polarization. Pro-1 provides a proton at C2. The involvement of His-28 and, Tyr-103' distinguishes the cis-CaaD mechanism from the otherwise parallel, CaaD mechanism. The two mechanisms probably evolved independently as the, result of an early gene duplication of a common ancestor.
About this Structure
2FLT is a Single protein structure of sequence from Coryneform bacterium with as ligand. Full crystallographic information is available from OCA.
Reference
Crystal structures of native and inactivated cis-3-chloroacrylic acid dehalogenase. Structural basis for substrate specificity and inactivation by (R)-oxirane-2-carboxylate., de Jong RM, Bazzacco P, Poelarends GJ, Johnson WH Jr, Kim YJ, Burks EA, Serrano H, Thunnissen AM, Whitman CP, Dijkstra BW, J Biol Chem. 2007 Jan 26;282(4):2440-9. Epub 2006 Nov 22. PMID:17121835
Page seeded by OCA on Tue Jan 29 19:39:38 2008
