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Crystal structure of the haloalcohol dehalogenase HheC complexed with the haloalcohol mimic (R)-1-para-nitro-phenyl-2-azido-ethanol

Overview

Haloalcohol dehalogenases are bacterial enzymes that catalyze the, cofactor-independent dehalogenation of vicinal haloalcohols such as the, genotoxic environmental pollutant 1,3-dichloro-2-propanol, thereby, producing an epoxide, a chloride ion and a proton. Here we present X-ray, structures of the haloalcohol dehalogenase HheC from Agrobacterium, radiobacter AD1, and complexes of the enzyme with an epoxide product and, chloride ion, and with a bound haloalcohol substrate mimic. These, structures support a catalytic mechanism in which Tyr145 of a Ser-Tyr-Arg, catalytic triad deprotonates the haloalcohol hydroxyl function to generate, an intramolecular nucleophile that substitutes the vicinal halogen., Haloalcohol dehalogenases are related to the widespread family of, NAD(P)H-dependent short-chain dehydrogenases/reductases (SDR family), which use a similar Ser-Tyr-Lys/Arg catalytic triad to catalyze reductive, or oxidative conversions of various secondary alcohols and ketones. Our, results reveal the first structural details of an SDR-related enzyme that, catalyzes a substitutive dehalogenation reaction rather than a redox, reaction, in which a halide-binding site is found at the location of the, NAD(P)H binding site. Structure-based sequence analysis reveals that the, various haloalcohol dehalogenases have likely originated from at least two, different NAD-binding SDR precursors.

About this Structure

1PX0 is a Single protein structure of sequence from Agrobacterium tumefaciens with RPN as ligand. Full crystallographic information is available from OCA.

Reference

Structure and mechanism of a bacterial haloalcohol dehalogenase: a new variation of the short-chain dehydrogenase/reductase fold without an NAD(P)H binding site., de Jong RM, Tiesinga JJ, Rozeboom HJ, Kalk KH, Tang L, Janssen DB, Dijkstra BW, EMBO J. 2003 Oct 1;22(19):4933-44. PMID:14517233

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