6vo8
X-ray structure of the Cj1427 in the presence of NADH and GDP-D-glycero-D-mannoheptose, an essential NAD-dependent dehydrogenase from Campylobacter jejuni
Structural highlights
FunctionGMHD_CAMJE NAD-dependent dehydrogenase involved in the biosynthesis of heptose moieties with a hydroxyl group at C6 found on the capsular polysaccharide (CPS) of C.jejuni. Catalyzes the initial oxidation of C4 of the GDP-D-glycero-alpha-D-manno-heptose to form GDP-D-glycero-4-keto-alpha-D-lyxo-heptose in the presence of alpha-ketoglutarate required to recycle the NADH nucleotide.[1] Publication Abstract from PubMedMany strains of Campylobacter jejuni display modified heptose residues in their capsular polysaccharides (CPS). The precursor heptose was previously shown to be GDP-d-glycero-alpha-d-manno-heptose, from which a variety of modifications of the sugar moiety have been observed. These modifications include the generation of 6-deoxy derivatives and alterations of the stereochemistry at C3-C6. Previous work has focused on the enzymes responsible for the generation of the 6-deoxy derivatives and those involved in altering the stereochemistry at C3 and C5. However, the generation of the 6-hydroxyl heptose residues remains uncertain due to the lack of a specific enzyme to catalyze the initial oxidation at C4 of GDP-d-glycero-alpha-d-manno-heptose. Here we reexamine the previously reported role of Cj1427, a dehydrogenase found in C. jejuni NTCC 11168 (HS:2). We show that Cj1427 is co-purified with bound NADH, thus hindering catalysis of oxidation reactions. However, addition of a co-substrate, alpha-ketoglutarate, converts the bound NADH to NAD(+). In this form, Cj1427 catalyzes the oxidation of l-2-hydroxyglutarate back to alpha-ketoglutarate. The crystal structure of Cj1427 with bound GDP-d-glycero-alpha-d-manno-heptose shows that the NAD(H) cofactor is ideally positioned to catalyze the oxidation at C4 of the sugar substrate. Additionally, the overall fold of the Cj1427 subunit places it into the well-defined short-chain dehydrogenase/reductase superfamily. The observed quaternary structure of the tetrameric enzyme, however, is highly unusual for members of this superfamily. Structural Analysis of Cj1427, an Essential NAD-Dependent Dehydrogenase for the Biosynthesis of the Heptose Residues in the Capsular Polysaccharides of Campylobacter jejuni.,Huddleston JP, Anderson TK, Spencer KD, Thoden JB, Raushel FM, Holden HM Biochemistry. 2020 Mar 23. doi: 10.1021/acs.biochem.0c00096. PMID:32168450[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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