1zmt
Structure of haloalcohol dehalogenase HheC of Agrobacterium radiobacter AD1 in complex with (R)-para-nitro styrene oxide, with a water molecule in the halide-binding site
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OverviewOverview
Halo alcohol dehalogenase HheC catalyzes the highly enantioselective, dehalogenation of vicinal halo alcohols to epoxides, as well as the, reverse reaction, the enantioselective and beta-regioselective, nucleophilic ring opening of epoxides by pseudo-halides such as azide and, cyanide. To investigate this latter reaction, we determined X-ray, structures of complexes of HheC with the favored and unfavored enantiomers, of para-nitrostyrene oxide. The aromatic parts of the two enantiomers bind, in a very similar way, but the epoxide ring of the unfavored, (S)-enantiomer binds in a nonproductive inverted manner, with the epoxide, oxygen and Cbeta atom positions interchanged with respect to those of the, favored (R)-enantiomer. The calculated difference in relative Gibbs, binding energy is in agreement with the observed loss of a single hydrogen, bond in the S bound state with respect to the R bound state. Our results, indicate that it is the nonproductive binding of the unfavored, (S)-enantiomer, rather than the difference in affinity for the two, enantiomers, that allows HheC to catalyze the azide-mediated ring opening, of para-nitrostyrene oxide with high enantioselectivity. This work, represents a rare opportunity to explain the enantioselectivity of an, enzymatic reaction by comparison of crystallographic data on the binding, of both the favored and unfavored enantiomers.
About this StructureAbout this Structure
1ZMT is a Single protein structure of sequence from Agrobacterium tumefaciens with as ligand. Full crystallographic information is available from OCA.
ReferenceReference
Structural basis for the enantioselectivity of an epoxide ring opening reaction catalyzed by halo alcohol dehalogenase HheC., de Jong RM, Tiesinga JJ, Villa A, Tang L, Janssen DB, Dijkstra BW, J Am Chem Soc. 2005 Sep 28;127(38):13338-43. PMID:16173767
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