- Supramolecular organization of the metabolic pathways
In eukaryotic and more recently in prokaryotic cells, complexes or proteins involved in the same physiological pathways have been shown to be associated in large macromolecular complexes. Our objective is to address the central question of the organization, the dynamics and functionalities of biological macromolecules complexes, including their interactions within the membrane, or their interaction with lipids. Regulation of the respiratory chains, reciprocal stabilization of individual respiratory enzymes or complexes, existence and role of accessory proteins in supercomplexes formation/stabilization or even modifications of the intrinsic properties of proteins depending on their association state represent the main goal of our current research.
Two main energetic metabolisms are currently study in the lab:
1- Aquifex aeolicus energetic metabolism
We have successfully used a proteomic approach to better characterized functional respiratory complexes as well as identify novels protein-protein interactions in membranes of the hyperthermophilic bacterium Aquifex aeolicus. Using biochemical techniques, two respiratory supercomplexes have been purified and characterized: the first one is involved in H2S oxidation coupled to O2 reduction, the second one is involved in the H2/Sulfur pathway.
Model of the H2, O2 and sulfur energetic metabolism in Aquifex aeolicus
2- Ferrous ion energetic metabolism by acidophilic microorganisms
We used A. ferroxidans as a model organism to study life under low pH. One of our main aim is to understand the metabolism, conformation and stability of metalloproteins in the low pH environment of the periplasm of such bacteria (pH 2). Our research focuses on: i) the supramolecular organization of ferrous iron oxidation pathway by A. ferrooxidans bacterium and Ferroplasma acidiphilum archae, and ii) the role of accessory proteins in supercomplexes.
The presence of a supercomplex spanning both the inner and the outer membrane has been discovered in A. ferrooxidans. Further functional study show that this supercomplex correspond to a respirasome allowing electron transfer from the first iron electron acceptor present in the external membrane to the final enzyme present in the inner membrane that allow the reduction of the oxygen. In F. acidiphilum, two macromolecular complexes, able to reduce oxygen using ferrous iron as electron donor were isolated.
The iron oxidase-oxygen reductase supercomplex from Acidithiobacillus ferrooxidans
Collaborations: IBS Grenoble, IRD Marseille, ILL Grenoble, Helmholtz Centre for Infection Research Braunschweig (Germany).
Facilities: Proteomics facilities from the Institute (IFR88) Proteomic Analysis Centre (mass spectrometers, proteins sequencer, FFE), oxygraph oxygen electrodes, EPR, Fermentation Plant unit from the Institute.