title: Crystal structures of native and inactivated cis-3-chloroacrylic acid dehalogenase: Implications for the catalytic and inactivation mechanisms.
abstract: The isomeric mixture of cis- and trans-1,3-dichloropropene constitutes the active component of a widely used nematocide known as Telone II®. The mixture is processed by various soil bacteria to acetaldehyde through the 1,3-dichloropropene catabolic pathway. The pathway relies on an isomer-specific hydrolytic dehalogenation reaction catalyzed by cis- or trans-3-chloroacrylic acid dehalogenase, known respectively as cis-CaaD and CaaD. Previous sequence analysis and crystallographic studies of the native and covalently modified enzymes identified Pro-1, His-28, Arg-70, Arg-73, Tyr-103, and Glu-114 as key binding and catalytic residues in cis-CaaD. Mutagenesis of these residues confirmed their importance to the dehalogenation reaction. Crystal structures of the native enzyme (2.01Å resolution) and the enzyme covalently modified at the Pro-1 nitrogen by 2-hydroxypropanoate (1.65Å resolution) are reported here. Both structures are at a resolution higher than previously reported (2.75Å and 2.1Å resolution, respectively). The conformation of the covalent adduct is strikingly different from that previously reported due to its interaction with a 7-residue loop (Thr-32 to Leu-38). The participation of another active site residue, Arg-117, in catalysis and inactivation was also examined. The implications of the combined findings for the mechanisms of catalysis and inactivation are discussed.
authors.affiliation: Division of Medicinal Chemistry, College of Pharmacy, University of Texas, Austin, TX 78712, USA.
authors.forename: Youzhong
authors.initials: Y
authors.lastname: Guo
authors.forename: Hector
authors.initials: H
authors.lastname: Serrano
authors.forename: William H
authors.initials: WH
authors.lastname: Johnson
authors.forename: Stephen
authors.initials: S
authors.lastname: Ernst
authors.forename: Marvin L
authors.initials: ML
authors.lastname: Hackert
authors.forename: Christian P
authors.initials: CP
authors.lastname: Whitman
mesh_terms: D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D004926:Escherichia coli / Q000201:enzymology*; D006867:Hydrolases / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D009154:Mutation
chemical_list: D004791:Enzyme Inhibitors; D006867:Hydrolases; C077719:cis-3-chloroacrylic acid dehalogenase