Cédric ORELLE, research director within the ATP/Bacterial GTPases team: antibiotic resistance and new enzymes, Molecular Microbiology and Structural Biochemistry (MMSB) UMR 5086 CNRS, University of Lyon

I hold a PhD in Biochemistry and have been a researcher at CNRS since 2015. I am interested in the mechanisms of resistance to antibiotics and antimicrobial peptides in bacteria. In particular, I study the molecular mechanism of ABC family transporters that use the energy of ATP hydrolysis to confer resistance, often through an efflux mechanism. For this I use biochemical approaches (for example site-directed mutagenesis, purification and reconstitution of membrane proteins into liposomes or nanodiscs, measurements of enzymatic activities, deuterium/hydrogen exchange coupled with mass spectrometry), biophysical (fluorescence, EPR) and structural (cryoEM, NMR).

We used the RPE equipment of the BIP laboratory platform (Bioenergetics and Protein Engineering, in Marseille) to study the conformational changes of a multidrug ABC transporter called BmrA (Panel A), in order to better understand its mechanism transport. For this, we combined the use of nitroxide-type paramagnetic probes and the measurement of distances between probes via the pulsed EPR approach called DEER (Double Electron-Electron Resonance).

Thanks to the DEER experiments, we were able to detect changes in distances at different positions of BmrA during its catalytic cycle (panels B and C). This allowed us to complete a biochemical and structural study on the degree of separation of the nucleotide binding domains during the BmrA transport cycle. An article is being submitted on this subject.

Platform used: BIP, CNRS/Aix-Marseille University