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Département Biochimie, Biophysique et Biologie Structurale

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  • Mardi 24 septembre 11:00-12:00 - Joanna Timmins - IBS, Univ. Grenoble Alpes, CNRS, CEA

    Nucleoid organisation and dynamics in Deinococcus radiodurans

    Résumé : In all organisms, genomic DNA is compacted several orders of magnitude and yet must remain accessible for essential DNA-related processes. Using a combination of biochemical, biophysical and advanced imaging approaches, we have explored the nucleoid organization in Deinococcus radiodurans, a relatively large, spherical bacterium, well-known for its exceptional radioresistance. This work has revealed that its nucleoid is highly compact, but also surprisingly dynamic, adopting various configurations, including the previously described toroid. A major player in the organization of bacterial nucleoids is the highly abundant histone-like HU protein that largely coats the genomic DNA. We have investigated HU’s mode of DNA binding and its ability to condense the genomic DNA. Taken together, these findings demonstrate that bacterial nucleoids are tightly regulated by cell shape and cell cycle progression, and suggest that the HU protein plays a key role in this process.

    Lieu : Salle de conférence - Bat 144, Campus CEA Saclay

  • Vendredi 4 octobre 11:00-12:00 - Ji-Shen ZHENG - University of Science and Technology of China, Hefei, China

    Chemical synthesis of membrane proteins and their biological applications

    Résumé : Chemical protein synthesis may enable the preparation of proteins with predesigned structures at atomic precision, thus permitting the acquisition of otherwise difficult-to-obtain proteins bearing either post-translational modification or site-specific labeling for advanced studies. Chemical synthesis of water-soluble globular proteins has been well developed and applied to biochemical and pharmaceutical studies.
    Membrane proteins are responsible for the substance transport, information exchange and enzyme catalysis, and are critical for cell growth and development, immune response and other processes. However, the highly important class of membrane proteins such as multiple membrane-spanning ion channels and drug transporters remains challenging to chemical synthesis owing to their hydrophobic nature and tendency to form aggregates.
    To overcome the problem, we developed the removable backbone modification (RBM) strategy for the chemical synthesis of membrane proteins. The RBM-modified membrane protein segments behave almost the same as ordinary water-soluble peptides in terms of Fmoc solid-phase synthesis, ligation, purification, and mass spectrometry characterization. The solubilizing RBM is straightforward to install at all amino acid sites except proline during the synthesis of transmembrane regions and facile to remove once synthesis of the peptide is complete.
    The RBM strategy was successfully prepared a series of difficult-to-obtain membrane proteins by biological expression method or membrane protein probes labeled with isotopes or fluorescence, including : (1) the homotetramer Kir5.1 ion channel transmembrane domain with K+ conductivity ; (2) the site-specific isotope-labeled hepatitis C virus ion channel p7 ; (3) the post-translationally modified membrane proteins (e.g. S-palmitoylated sarcolipin and M2 ion channel from Influenza A virus). These custom-made membrane protein samples provide unique molecular tools for the study of their structure, function and mechanism of action.
    For information, please contact, Nadège Jamin, Véronica Beswick or Cédric Montigny (I2BC / B3S / LPSM)

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

  • Mardi 24 septembre 14:00-17:00 - Jingqi DAI - Equipe Enveloppe Nucléaire, Télomères et Réparation de l'ADN, I2BC

    Mécanisme moléculaire de l’endonucléase Mlh1-Mlh3 dans la voie de réparation des mésappariements de l’ADN et dans les processus de recombinaison en méiose

    Lieu : amphithéatre Bloch - Orme des Merisiers (CEA, accès libre)

    Notes de dernières minutes : Accès amphithéatre :

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