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4 octobre 2019: 2 événements

  • Département Biologie des Génomes

    Vendredi 4 octobre 11:00-12:00 - Johan DECELLE - Plant and Cell Physiology lab, Université Grenoble

    Algal farming in planktonic symbiosis through structural and metabolic transformation

    Résumé : Photosymbiosis between single-celled hosts and microalgae is widely distributed in the oceanic plankton. However, the functioning of this ecologically-important interaction remains enigmatic, particularly the mechanisms that allow the host cell to exploit its intracellular microalgae. Here, using a combination of single-cell structural (3D electron microscopy) and chemical imaging (nanoSIMS, synchrotron X-ray fluorescence), we show how the host reconfigures the photosynthetic machinery and metabolism of its microalgae. Within the host, photosynthetic efficiency is enhanced and the volume of algal cells increases up to ten times with a higher number of chloroplasts. Subcellular mapping of nutrients and N/P ratios shows that symbiotic microalgae are limited in phosphorous, and are transformed into an energy-acquisition machinery. The host also supplies a substantial amount of metals (iron and cobalt) that are stored in high concentration in algal vacuoles. Overall, this study sheds the light on host mechanisms to engineer microalgae in the oceanic plankton. In the near future, we plan to conduct transcriptomics, proteomics and metabolomics studies to better understand the symbiotic interaction, and compare with other photosymbiosis models in freshwater habitats, such as the ciliate Paramecium with the green alga Chlorella.

    Contact : Mireille BETERMIER (mireille.betermier

    Lieu : Salle des séminaires - bâtiment 26 - campus de Gif-sur-Yvette

    En savoir plus : Département Biologie des Génomes
  • Département Biochimie, Biophysique et Biologie Structurale

    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

    En savoir plus : Département Biochimie, Biophysique et Biologie Structurale