title: Identification of an unusual [2Fe-2S]-binding motif in the CDP-6-deoxy-D-glycero-l-threo-4-hexulose-3-dehydrase from Yersinia pseudotuberculosis: implication for C-3 deoxygenation in the biosynthesis of 3,6-dideoxyhexoses.
abstract: CDP-6-deoxy-L-threo-D-glycero-4-hexulose-3-dehydrase (E(1)) catalyzes the C-3 deoxygenation in the biosynthesis of 3,6-dideoxyhexoses in Yersinia pseudotuberculosis. E(1) is a pyridoxamine 5'-phosphate (PMP)-dependent enzyme that also contains a [2Fe-2S] center. This iron-sulfur cluster is catalytically essential, since removal of the [2Fe-2S] center leads to inactive enzyme. To identify the [2Fe-2S] core in E(1) and to study the effect of impairing the iron-sulfur cluster on the activity of E(1), a series of E(1) cysteine mutants were constructed and their catalytic properties were characterized. Our results show that E(1) displays a cluster-binding motif (C-X(57)-C-X(1)-C-X(7)-C) that has not been observed previously for [2Fe-2S] proteins. The presence of such an unusual iron-sulfur cluster in E(1), along with the replacement of the active site lysine by a histidine residue (H220), reflects a distinct evolutionary path for this enzyme. The cysteine residues (C193, C251, C253, C261) implicated in the binding of the iron-sulfur cluster in E(1) are conserved in the sequences of its homologues. It is likely that E(1) and its homologues constitute a new subclass in the family of iron-sulfur proteins, which are distinguished not only by their cluster ligation patterns but also by the chemistry used in catalyzing a simple, albeit mechanistically challenging, reaction.
authors.affiliation: Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712, USA.
authors.forename: Gautam
authors.initials: G
authors.lastname: Agnihotri
authors.forename: Yung-nan
authors.initials: YN
authors.lastname: Liu
authors.forename: Beth M
authors.initials: BM
authors.lastname: Paschal
authors.forename: Hung-wen
authors.initials: HW
authors.lastname: Liu
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002384:Catalysis; D003545:Cysteine / Q000235:genetics; D004789:Enzyme Activation / Q000235:genetics; D006601:Hexoses / Q000096:biosynthesis*; D006836:Hydro-Lyases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007501:Iron / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D011733:Pyridoxamine / Q000031:analogs & derivatives* / Q000378:metabolism; D016415:Sequence Alignment; D015011:Yersinia pseudotuberculosis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D006601:Hexoses; D007506:Iron-Sulfur Proteins; D008024:Ligands; C023708:abequose; D011733:Pyridoxamine; D007501:Iron; D010088:Oxidoreductases; C099976:CDP-6-deoxy-4-hexulose-3-dehydrase reductase; C073141:CDP-4-keto-6-deoxy-D-glucose-3-dehydrase; D006836:Hydro-Lyases; D003545:Cysteine; C010627:pyridoxamine phosphate