2bgj

File:2bgj.gif

spinqualitylabelsall models 2bgj, resolution 2.10Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

X-RAY STRUCTURE OF THE FERREDOXIN-NADP(H) REDUCTASE FROM RHODOBACTER CAPSULATUS AT 2.1 ANGSTROMS

OverviewOverview

The photosynthetic bacterium Rhodobacter capsulatus contains a ferredoxin, (flavodoxin)-NADP(H) oxidoreductase (FPR) that catalyzes electron transfer, between NADP(H) and ferredoxin or flavodoxin. The structure of the enzyme, determined by X-ray crystallography, contains two domains harboring the, FAD and NADP(H) binding sites, as is typical of the FPR structural family., The FAD molecule is in a hairpin conformation in which stacking, interactions can be established between the dimethylisoalloxazine and, adenine moieties. The midpoint redox potentials of the various transitions, undergone by R. capsulatus FPR were similar to those reported for their, counterparts involved in oxygenic photosynthesis, but its catalytic, activity is orders of magnitude lower (1-2 s(-)(1) versus 200-500 s(-)(1)), as is true for most of its prokaryotic homologues. To identify the, mechanistic basis for the slow turnover in the bacterial enzymes, we, dissected the R. capsulatus FPR reaction into hydride transfer and, electron transfer steps, and determined their rates using stopped-flow, methods. Hydride exchange between the enzyme and NADP(H) occurred at, 30-150 s(-)(1), indicating that this half-reaction does not limit FPR, activity. In contrast, electron transfer to flavodoxin proceeds at 2.7, s(-)(1), in the range of steady-state catalysis. Flavodoxin semiquinone, was a better electron acceptor for FPR than oxidized flavodoxin under both, single turnover and steady-state conditions. The results indicate that, one-electron reduction of oxidized flavodoxin limits the enzyme activity, in vitro, and support the notion that flavodoxin oscillates between the, semiquinone and fully reduced states when FPR operates in vivo.

About this StructureAbout this Structure

2BGJ is a Single protein structure of sequence from Rhodobacter capsulatus with as ligand. Active as Ferredoxin--NADP(+) reductase, with EC number 1.18.1.2 Known structural/functional Site: . Full crystallographic information is available from OCA.

ReferenceReference

The ferredoxin-NADP(H) reductase from Rhodobacter capsulatus: molecular structure and catalytic mechanism., Nogues I, Perez-Dorado I, Frago S, Bittel C, Mayhew SG, Gomez-Moreno C, Hermoso JA, Medina M, Cortez N, Carrillo N, Biochemistry. 2005 Sep 6;44(35):11730-40. PMID:16128574

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