On behalf of Djemel Hamdane
Please find below a 2 years post-doc opportunity at College de France, Paris, France, in the Djemel HAMDANE group in the Laboratoire de Chimie des Processus Biologiques directed by Marc Fontecave http://www.college-de-france.fr/site/chimie-processus-biologiques/index.htm A 24‐month post‐doctoral position is available in the Djemel Hamdane team in the “Laboratoire de Chimie des Processus Biologiques” (Dir: Pr Marc Fontecave) at Collège de France, Paris (France) for a highly motivated and skilled post‐doctoral fellow who will have strong expertise in protein biochemistry and structural biology, in particular in crystallographic studies. The project will consist in the biochemical and structural investigation of several flavoenzymes proteins whose function is important for tRNA modification and maturation. Context: Our goal is to understand the molecular basis regarding some human mitochondrial disorders associated to defects in the post-transcriptional chemical modifications of mitochondrial tRNAs (MELAS syndrome, MERFF syndrome, and hypertrophic cardiomyopathies with lactic acidosis). Two groups of mutations affecting the modification of the wobble position U34 (5-taurinomethyluridine U34 (τm5U34)) in tRNAs have been identified so far. The first one consists of mutations in genes encoding for mitochondrial tRNAs that might affect their interaction with the GTPBP3/MTO1 enzymatic complex, which is responsible for the chemical modification of U34 mentioned above. The second group affects directly the mto1 and gtpbp3 genes. The human GTPBP3/MTO1 complex is homologous to the bacterial MnmE/MnmG complex. Although the bacterial system has shown to use several substrates and cofactors that are GTP, K+, glycine and methylenetetrahydrofolate for RNA modification, concerning the human counterpart there is to date no biochemical characterization reported so far in the literature. Currently, the structures of these RNA-modifying complexes are not available yet. Interestingly, the flavoprotein components of these enzymatic complexes, MnmG and MTO1, are paralogous to TrmFO meaning that they have a common ancestor but they acquired divergent functions. We have recently studied the enzyme mechanism of TrmFO from B. subtilis which employs the methylenetetrahydrofolate (CH2THF) as a methylene donor, and we have identified a unique methylene-iminium derivative of FAD (CH2=FAD) that is issued from the nucleophilic reaction of N5-FADH- onto CH2THF during the methyltransferase catalytic cycle. Currently, the structures of these RNA-modifying complexes are not available yet. Post-doctoral project: The post‐doctoral fellow will be involved in the structural and functional investigation of two enzymes involved in tRNA modification in the position U34. The objectives of our project are the following ones: (i) the biochemical and structural studies of the wild-type complex GTPBP3/MTO1 as well as its enzymatic activity of mitochondrial tRNA modification and (ii) the investigation, at the molecular level, of the effects of the pathogenic mutations in GTPBP3 and MTO1. For that project, we will use a judicious combination of biochemical and classical enzymology approaches, as well as crystallographic studies and state-of-the-art spectroscopic instrumentations (stopped-flow, rapid-quench, dichroism circular, etc) to uncover the complex enzymatic mechanism. The project will involve collaboration with the geneticist D. Brégeon, UPMC (Paris 6) for in vivo approaches. The “Laboratoire de Chimie des Processus Biologiques” offers state of the art equipements for X‐ray crystallography (in a glovebox for oxygen-free environment) and spectroscopies (UV‐visible absorption spectroscopy, fluorescence spectroscopy stopped‐flow, dichroïsm cicular, dynamic light scattering). Requirements: Candidates must have a recent Ph.D. in biochemistry, biophysics, or crystallography. Knowledge and experience of RNA and/or flavoproteins will be an advantage. Application: will include: (i) a cover letter outlining the applicant’s relevant research experience and motivation for applying to the position, (ii) a detailed CV (iii) the names of professional references. The position is available immediately with preferred starting dates in September-October 2017 Applications should be sent to: Dr Djemel Hamdane (djemel.hamdane@college‐de‐france.fr)
