1ofg

OverviewOverview

BACKGROUND: The organism Zymomonas mobilis occurs naturally in sugar-rich, environments. To protect the bacterium against osmotic shock, the, periplasmic enzyme glucose-fructose oxidoreductase (GFOR) produces the, compatible, solute sorbitol by reduction of fructose, coupled with the, oxidation of glucose to gluconolactone. Hence, Z mobilis can tolerate high, concentrations of sugars and this property may be useful in the, development of an efficient microbial process for ethanol production. Each, enzyme subunit contains tightly associated NADP which is not released, during the catalytic cycle. RESULTS: The structure of GFOR was determined, by X-ray crystallography at 2.7 A resolution. Each subunit of the, tetrameric enzyme comprises two domains, a classical dinucleotide-binding, domain, and a C-terminal domain based on a predominantly antiparallel, nine-stranded beta sheet. In the tetramer, the subunits associate to form, two extended 18-stranded beta sheets, which pack against each other in a, face to face fashion, creating an extensive interface at the core of the, tetramer. An N-terminal arm from each subunit wraps around the, dinucleotide-binding domain of an adjacent subunit, covering the adenine, ring of NADP. CONCLUSIONS: In GFOR, the NADP is found associated with a, classical dinucleotide-binding domain in a conventional fashion. The NADP, is effectively buried in the protein-subunit interior as a result of, interactions with the N-terminal arm from an adjacent subunit in the, tetramer, and with a short helix from the C-terminal domain of the, protein. This accounts for NADP's inability to dissociate. The N-terminal, arm may also contribute to stabilization of the tetramer. The enzyme has, an unexpected structural similarity with the cytoplasmic enzyme, glucose-6-phosphate dehydrogenase (G6PD). We hypothesize that both enzymes, have diverged from a common ancestor. The mechanism of catalysis is still, unclear, but we have identified a conserved structural motif (Glu-Lys-Pro), in the active site of GFOR and G6PD that may be important for catalysis.

About this StructureAbout this Structure

1OFG is a Single protein structure of sequence from Zymomonas mobilis with NDP as ligand. Active as Glucose--fructose oxidoreductase, with EC number 1.1.99.28 Full crystallographic information is available from OCA.

ReferenceReference

The structure of glucose-fructose oxidoreductase from Zymomonas mobilis: an osmoprotective periplasmic enzyme containing non-dissociable NADP., Kingston RL, Scopes RK, Baker EN, Structure. 1996 Dec 15;4(12):1413-28. PMID:8994968

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