title: X-ray crystal structure of Escherichia coli taurine/alpha-ketoglutarate dioxygenase complexed to ferrous iron and substrates.
abstract: Taurine/alpha-ketoglutarate dioxygenase (TauD), a non-heme Fe(II) oxygenase, catalyses the conversion of taurine (2-aminoethanesulfonate) to sulfite and aminoacetaldehyde concurrent with the conversion of alpha-ketoglutarate (alphaKG) to succinate and CO(2). The enzyme allows Escherichia coli to use taurine, widely available in the environment, as an alternative sulfur source. Here we describe the X-ray crystal structure of TauD complexed to Fe(II) and both substrates, alphaKG and taurine. The tertiary structure and fold of TauD are similar to those observed in other enzymes from the broad family of Fe(II)/alphaKG-dependent oxygenases, with closest structural similarity to clavaminate synthase. Using the TauD coordinates, a model was determined for the closely related enzyme 2,4-dichlorophenoxyacetate/alphaKG dioxygenase (TfdA), supporting predictions derived from site-directed mutagenesis and other studies of that biodegradative protein. The TauD structure and TfdA model define the metal ligands and the positions of nearby aromatic residues that undergo post-translational modifications involving self-hydroxylation reactions. The substrate binding residues of TauD were identified and those of TfdA predicted. These results, along with sequence alignment information, reveal how TauD selects a tetrahedral substrate anion in preference to the planar carboxylate selected by TfdA, providing insight into the mechanism of enzyme catalysis.
authors.affiliation: Dyson Perrins Laboratory, Oxford University, South Parks Road, Oxford, England, OX1 3QY, and Departments of Microbiology & Molecular Genetics and Biochemistry & Molecular Biology, Michigan State University, East Lansing, Michigan 48824-1011.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Elkins
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Ryle
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Clifton
authors.forename: Julie C
authors.initials: JC
authors.lastname: Dunning Hotopp
authors.forename: John S
authors.initials: JS
authors.lastname: Lloyd
authors.forename: Nicolai I
authors.initials: NI
authors.lastname: Burzlaff
authors.forename: Jack E
authors.initials: JE
authors.lastname: Baldwin
authors.forename: Robert P
authors.initials: RP
authors.lastname: Hausinger
authors.forename: Peter L
authors.initials: PL
authors.lastname: Roach
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D002384:Catalysis; D003460:Crystallization; D018360:Crystallography, X-Ray; D019281:Dimerization; D004926:Escherichia coli / Q000201:enzymology*; D005296:Ferrous Compounds / Q000737:chemistry* / Q000378:metabolism; D007656:Ketoglutaric Acids / Q000737:chemistry / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational; D017433:Protein Structure, Secondary; D013379:Substrate Specificity; D013654:Taurine / Q000737:chemistry* / Q000378:metabolism
chemical_list: D005296:Ferrous Compounds; D007656:Ketoglutaric Acids; D013654:Taurine; D015084:2,4-Dichlorophenoxyacetic Acid; D006899:Mixed Function Oxygenases; C084087:2,4-dichlorophenoxyacetate-alpha-ketoglutarate dioxygenase; C433064:taurine-alpha-ketoglutarate dioxygenase