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Dive into the research topics where Marie‐Hélène Charon is active.

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Featured researches published by Marie‐Hélène Charon.


Nature Structural & Molecular Biology | 1999

Crystal structures of the key anaerobic enzyme pyruvate:ferredoxin oxidoreductase, free and in complex with pyruvate

Eric Chabriere; Marie‐Hélène Charon; Anne Volbeda; Laetitia Pieulle; E.C Hatchikian; Juan C. Fontecilla-Camps

Oxidative decarboxylation of pyruvate to form acetyl–coenzyme A, a crucial step in many metabolic pathways, is carried out in most aerobic organisms by the multienzyme complex pyruvate dehydrogenase. In most anaerobes, the same reaction is usually catalyzed by a single enzyme, pyruvate:ferredoxin oxidoreductase (PFOR). Thus, PFOR is a potential target for drug design against certain anaerobic pathogens. Here, we report the crystal structures of the homodimeric Desulfovibrio africanus PFOR (data to 2.3 Å resolution), and of its complex with pyruvate (3.0 Å resolution). The structures show that each subunit consists of seven domains, one of which affords protection against oxygen. The thiamin pyrophosphate (TPP) cofactor and the three [4Fe–4S] clusters are suitably arranged to provide a plausible electron transfer pathway. In addition, the PFOR–pyruvate complex structure shows the noncovalent fixation of the substrate before the catalytic reaction.


EMBO Reports | 2000

A redox-dependent interaction between two electron-transfer partners involved in photosynthesis

Renaud Morales; Marie‐Hélène Charon; Galina Kachalova; Laurence Serre; Milagros Medina; Carlos Gómez-Moreno; Michel Frey

Ferredoxin:NADP+:reductase (FNR) catalyzes one terminal step of the conversion of light energy into chemical energy during photosynthesis. FNR uses two high energy electrons photoproduced by photosystem I (PSI) and conveyed, one by one, by a ferredoxin (Fd), to reduce NADP+ to NADPH. The reducing power of NADPH is finally involved in carbon assimilation. The interaction between oxidized FNR and Fd was studied by crystallography at 2.4 Å resolution leading to a three‐dimensional picture of an Fd–FNR biologically relevant complex. This complex suggests that FNR and Fd specifically interact prior to each electron transfer and disassemble upon a redox‐linked conformational change of the Fd.


Current Opinion in Structural Biology | 1999

Structure and electron transfer mechanism of pyruvate:ferredoxin oxidoreductase

Marie‐Hélène Charon; Anne Volbeda; Eric Chabriere; Laetitia Pieulle; Juan C. Fontecilla-Camps

The first crystal structure of pyruvate:ferredoxin oxidoreductase to be determined has provided significant new information on its structural organization and redox chemistry. Spectroscopic analyses of a radical reaction intermediate have shed more light on its thiamin-based mechanism of catalysis. Different approaches have been used to study the interaction between the enzyme and ferredoxin, its redox partner.


Acta Crystallographica Section D-biological Crystallography | 2000

Crystallographic studies of the interaction between the ferredoxin-NADP+ reductase and ferredoxin from the cyanobacterium Anabaena: looking for the elusive ferredoxin molecule.

Renaud Morales; Galina Kachalova; Frédéric M. D. Vellieux; Marie‐Hélène Charon; Michel Frey

Ferredoxin-NADP(+) reductase (FNR) and its physiological electron donor ferredoxin (Fd) from the cyanobacterium Anabaena PCC7119 have been co-crystallized. The unit-cell parameters are a = b = 63.72, c = 158.02 A and the space group is P2(1)2(1)2(1). The crystal structure has been solved with 2.4 A resolution synchrotron data by molecular replacement, anomalous dispersion and R(min) search methods. For the computations, the crystal was treated as a merohedral twin. The asymmetric unit contains two FNR molecules and one ferredoxin molecule. The packing of the FNR molecules displays a nearly tetragonal symmetry (space group P4(3)2(1)2), whereas the ferredoxin arrangement is orthorhombic. This study provides the first crystallographic model of a dissociable complex between FNR and Fd.


Acta Crystallographica Section D-biological Crystallography | 1999

Crystallization and preliminary crystallographic analysis of the pyruvate–ferredoxin oxidoreductase from Desulfovibrio africanus

Laetitia Pieulle; Eric Chabriere; Claude E. Hatchikian; Juan C. Fontecilla-Camps; Marie‐Hélène Charon

For the first time, crystals of a pyruvate-ferredoxin oxidoreductase (PFOR) suitable for X-ray analysis have been obtained. This enzyme catalyzes, in anaerobic organisms, the crucial energy-yielding reaction of pyruvate decarboxylation to acetylCoA. Polyethylene glycol and divalent metal cations have been used to crystallize the PFOR from the sulfate-reducing bacterium Desulfovibrio africanus. Two different orthorhombic (P212121 ) crystal forms have been grown with unit-cell dimensions a = 86.1, b = 146.7, c = 212.5 A and a = 84.8, b = 144.9, c = 203.0 A. Both crystals diffract to 2.3 A resolution using synchrotron radiation.


Acta Crystallographica Section D-biological Crystallography | 1999

Combination of methods used in the structure solution of pyruvate:ferredoxin oxidoreductase from two crystal forms

Eric Chabriere; Anne Volbeda; Juan-Carlos Fontecilla-Camps; M. Roth; Marie‐Hélène Charon

The structure of the homodimeric 267 kDa pyruvate:ferredoxin oxidoreductase (PFOR) of Desulfovibrio africanus was solved with data from two crystals forms, both containing two monomers per asymmetric unit. Phases were obtained from multiwavelength anomalous dispersion (MAD), solvent flattening (SF), molecular replacement (MR) using a 5 A resolution electron-density search model, multiple isomorphous replacement (MIR) and, finally, electron-density averaging (DA) procedures. It is shown how the combination of all these techniques was used to overcome problems arising from incompleteness of MAD data and weak phasing power of MIR data. A real-space refinement (RSR) procedure is described to improve MR solutions and obtain very accurate protein envelopes and non-crystallographic symmetry (NCS) transformations from 5 A resolution phase information. These were crucial for the phase extension to high resolution by DA methods.


Acta Crystallographica Section D-biological Crystallography | 1999

PBR: a heavy-atom refinement and phasing ­procedure to reduce phase bias when heavy-atom derivatives contain common sites

Eric Chabriere; Marie‐Hélène Charon; Frédéric M. D. Vellieux

A procedure, called PBR (phase-bias reduction), has been developed to properly refine heavy-atom derivatives and to generate less biased heavy-atom phases when these derivatives contain common heavy-atom sites. Two independent events are obtained by splitting the refinement and phasing calculations into two stages, the first in which one of the derivatives having common sites is used together with the native amplitudes and the second in which both derivatives with common sites are used simultaneously, with one of them being used as the native data set. Improved centroid phases and the corresponding figures of merit are obtained by phase combination. This procedure has been used in the structure determination of the iron-cluster-containing protein -pyruvate-ferredoxin oxidoreductase. When the common heavy-atom sites are properly treated by the PBR procedure, the resulting calculated centroid phases are improved with respect to classical heavy-atom refinement centroid phases where all derivatives are refined together. This leads to improved electron-density distributions, since anomalous difference Fourier maps calculated with the PBR-refined centroid phases and corresponding figures of merit show more clearly the positions of the iron sites.


Biochemistry | 1999

Refined X-ray structures of the oxidized, at 1.3 A, and reduced, at 1.17 A, [2Fe-2S] ferredoxin from the cyanobacterium Anabaena PCC7119 show redox-linked conformational changes.

Renaud Morales; Marie‐Hélène Charon; Gilbert Hudry-Clergeon; Yves Pétillot; Sofie Norager; Milagros Medina; Michel Frey


FEBS Journal | 1999

Structural and kinetic studies of the pyruvate–ferredoxin oxidoreductase/ferredoxin complex from Desulfovibrio africanus

Laetitia Pieulle; Marie‐Hélène Charon; Pierre Bianco; Jacques Bonicel; Yves Pétillot; E. Claude Hatchikian


Protein Science | 1995

The effects of filtration on protein nucleation in different growth media

Joachim Hirschler; Marie‐Hélène Charon; Juan C. Fontecilla-Camps

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Eric Chabriere

Aix-Marseille University

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Juan C. Fontecilla-Camps

Centre national de la recherche scientifique

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Laetitia Pieulle

Centre national de la recherche scientifique

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Michel Frey

Centre national de la recherche scientifique

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Renaud Morales

Centre national de la recherche scientifique

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Anne Volbeda

Centre national de la recherche scientifique

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Yves Pétillot

Centre national de la recherche scientifique

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Frédéric M. D. Vellieux

Centre national de la recherche scientifique

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Galina Kachalova

Centre national de la recherche scientifique

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