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  • Génomes

    • Vendredi 6 avril 11:00-12:00 - Ed Tate - Imperial College London

      Proteins, lipids and drug discovery : from malaria to the common cold

      Résumé : My group develops chemical biology approaches to identify and validate potential drug targets, particularly in the field of protein post-translational modification. In this talk I will discuss our recent work in the field of protein lipidation (acylation, cholesterylation and prenylation), where we have contributed to validation of protein targets in infectious diseases caused by parasites (malaria, leishmaniasis, trypanosomiasis), bacteria and viruses, and in cancer. I will also illustrate how we have used chemical tagging technologies in an analytical platform for quantification and identification of protein lipidation in live cells and animals, providing the first insights into how lipidation changes in response to drug treatment at the whole proteome level. This research has enriched our understanding of these traditionally challenging classes of protein modification, and delivered novel small molecules into pre-clinical development.
      Contact : Carmela GIGLIONE <carmela.giglione i2bc.paris-saclay.fr>

      Lieu : Bibliothèque- bâtiment 34 - Campus CNRS de Gif-sur-Yvette

      Article

  • Biologie Cellulaire

    • Vendredi 6 avril 10:00-11:00 - Zofia CHRZANOWSKA LIGHTOWLERS - Newcastle University, invitée par N. Bonnefoy

      Human mitochondrial translation : what makes the proteins and how are they escorted to their final destination ?

      Résumé : The ribosome is the molecular machinery that synthesises proteins from template mRNA. Many features are common to ribosomes be they bacterial 70S particles, or 80S monosomes present in the eukaryotic cytosol. Although mitoribosomes have retained certain elements of the bacterial ribosome, both protein and rRNA, they have also diverged from the template in a number of ways. This is particularly true for human mitochondria that have been revealed by cryo-EM to have integrated unexpected components. These similarities, differences and some of the idiosyncrasies of the human mitoribosome will be described along with an example of the plasticity in the system, which is seen when things go wrong.

      Lieu : Bibliothèque, Bât. 34 - Campus de Gif-sur-Yvette

      Article

    • Vendredi 6 avril 10:00-11:00 - Robert LIGHTOWLERS - Newcastle University, invité par N. Bonnefoy

      Human mitochondrial translation : what makes the proteins and how are they escorted to their final destination ?

      Résumé : The function of human mitochondrial insertase Oxa1L, the human homolog of yeast Oxa1 (first described by members of CGM in Gif-Sur-Yvette) has remained contentious since its identification over 20 years ago. Recently, we have identified a patient with a biallelic mutation in OXA1L that causes a mitochondrial disease due to a combined oxidative phosphorylation deficiency. Previous experiments with shRNA depletion of human Oxa1L reported a defect in complexes I and V but spared any involvement in cytochrome c oxidase assembly (COX ; complex IV), a surprising result as Oxa1L had been expected to be essential for the insertion of all mtDNA encoded components. Patient muscle and fibroblasts show a decrease in Oxa1L but also a depletion of complex IV and V with a relative sparing of complex I, a phenotype rescued by expression of wild type Oxa1L. Targeted depletion of OXA1L in Drosophila melanogaster caused defects in the assembly of complexes I, IV and V. Targeted disruption of Oxa1L in human HEK293T cells required the co-expression of exogenous Oxa1L to prevent lethality, but the controlled loss of Oxa1L resulted in a substantial loss of complexes I, III, IV and V. Neuropathological experiments from the Oxa1L-deficient patient, however, indicate an isolated complex I deficiency. Taken together, whilst our data verify the pathogenicity of mutations in Oxa1L and demonstrate it is required for the assembly of multiple OXPHOS complexes, we find striking tissue and cell specific variation, perhaps implying the existence of other tissue-specific insertases involved in mitochondrial protein synthesis.

      Lieu : Bibliothèque, Bât. 34 - Campus de Gif-sur-Yvette

      Article

    • Vendredi 20 avril 11:00-12:00 - Eelco VAN ANKEN - San Raffaele Scientific Institute, Università Vita-Salute San Raffaele, Milan, Italy, invité par B. D'Autréaux

      How cells evaluate whether homeostatic readjustment in the endoplasmic reticulum is a success or failure

      Lieu : Bibliothèque - bâtiment 34 - Campus de Gif-sur-Yvette

      Article

  • I2BC

    • Mercredi 18 avril 11:30-13:00 - Pierre Gonczy - Ecole Polytechnique Fédérale de Lausanne, Suisse

      Mechanisms of centriole assembly

      Résumé : The centriole is a remarkable microtubule-based organelle that is essential for the formation of cilia, flagella and centrosomes. The centriole is organized around a nine-fold symmetrical cartwheel typically 100 nm in height, which is critical for the onset of organelle biogenesis. The cartwheel comprises a stack of ring-containing entities that each accommodates nine homodimers of SAS-6 proteins. In contrast to the knowledge about the self-assembly properties of SAS-6 proteins, the mechanisms enabling ring stacking are poorly understood. Furthermore, the assembly dynamics of SAS-6 ring-containing entities remains elusive.
      After introducing the subject matter, I will report notably on our development of a cell-free assay to address this important open question using the Chlamydomonas reinhardtii SAS-6 protein CrSAS-6. Using high-speed atomic force microscopy (AFM), we monitored the assembly dynamics of CrSAS-6 homodimers, and thus determined possible routes and kinetic rates for CrSAS-6 ring formation.


      Invité par Anne-Marie Tassin, équipe Biogénese et fonction des structures centriolaires et ciliaires

      Lieu : Auditorium I2BC - Bâtiment 21
      Campus CNRS de Gif-sur-Yvette

      Article

  • Microbiologie

    • Mardi 10 avril 11:30-13:00 - Dr. Marianne Ilbert - « Métabolisme énergétique des bactéries extrémophiles » Bioénergétique et Ingénierie des Protéines (BIP), Marseille

      Bacterial life in acid ? Toward a better understanding of an iron respiratory chain working at pH 2

      Résumé : Microorganisms are found in various ecosystems, where they have this incredible ability to adapt to challenging conditions. Acidithiobacillus ferrooxidans, a gram negative bacterium, is the most studied and relevant model to understand how to survive in harmful environments with pH as low as pH 2 and high level of toxic metals, getting energy source from minerals containing iron and sulfur. This remarkable ability to gain energy through oxidation of ferrous iron at low pH has driven a lot of interest because of application in microbial leaching. We are currently studying the iron respiratory chain of this acidophilic organism by a multidisciplinary approach. Several metalloproteins have been identified and characterized, but the electron transfer pathway from the outer membrane to the inner membrane cytochrome c oxidase is still obscure.
      During this seminar, we will first focus our attention on the newly identified cupredoxin, AcoP, which contains a green-type copper center. We will present the crystal structure of AcoP and will discuss its spectroscopic features underlying some unexpected properties. Key residues were targeted by site directed mutagenesis to better understand the determinants driving these unusual properties. In addition, we are currently reconstituting parts of the respiratory chain with the aim to determine step by step the electron transfer pathway. The strategy is to study purified AcoP, di-heme cytochrome c and cytochrome c oxidase alone or incubated together in solution or in the immobilized state at an electrode mimicking one of the partner. Beyond thermodynamic data for each protein, this methodology offers the opportunity to decipher the molecular basis of protein-protein interaction favorable to electron transfer at low pH (A. ferrooxidans periplasmic compartment is estimated at pH 2.5). This should allow us to further describe the function of each protein in this energy chain.
      Invitée par l’équipe Adaptation bactérienne aux changements environnementaux
      Contact : Anne Durand

      Lieu : Salle Kalogeropoulos - Bâtiment 400, Campus d’Orsay

      Article

  • cytoskeleton club

    • Mardi 10 avril 11:30-12:30 - Francesca Giordano

      Cytoskeleton club

      Résumé : Staying in touch : ORP5-mediated lipid exchange at ER-mitochondria contact sites and impact on mitochondria calcium homeostasis

      Lieu : Bibliothèque - Bâtiment 34, campus de Gif

      Article

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