CNRS - AIX MARSEILLE UNIV: UMR7257


Our laboratory


The Architecture et Fonction des Macromolécules Biologiques (AFMB) laboratory, overseen by the CNRS and AMU, is a center of structural biology localized on the Luminy campus in the South of Marseilles, France, and in partnership with INRA under contract. The aim of our researches is to depict the architecture of proteins or macromolecular assemblies at the molecular level to understand the biological mechanisms which they govern. The description of interactions between macromolecules or a macromolecule and a ligand is also crucial to manipulate these complex molecules. Finally, to understand the molecular diversity of members of some protein families, we also analyze the big data issued from large-scale genome sequencing centers.


Seminars
  • Thursday May 31 at 11am: Mark McBride, Department of Biological Sciences, University of Wisconsin-Milwaukee, WI, USA. "The Bacteroidetes do it differently: novel motility, protein secretion, and polysaccharide utilization machineries"

    Abstract (...)

    Abstract Flavobacterium johnsoniae and other members of the phylum Bacteroidetes have many unique features, including novel machinery for gliding motility, protein secretion, and polysaccharide utilization. Cells of Flavobacterium johnsoniae lack flagella and pili but actively move over surfaces by gliding motility. This appears unrelated to other bacterial gliding motility systems. Flavobacterium cell movement occurs when large motility adhesins, such as SprB, are rapidly propelled along the cell surface by the gliding motors, powered by the proton gradient across the cytoplasmic membrane. The adhesins travel the length of the cell along helical tracks. Binding of the adhesins to the substratum results in rotation and translocation of the cell. Cells have multiple motility adhesins allowing them to attach to and glide over diverse surfaces. The adhesins are delivered to the cell surface by the type IX protein secretion system (T9SS). T9SSs are common in but confined to the phylum Bacteroidetes. The gliding motility apparatus and the T9SS appear to be intertwined, and components of the T9SS may perform roles in both secretion and gliding. In addition to motility adhesins, T9SSs secrete many other cell-surface and soluble proteins. These include enzymes involved in digestion of polysaccharides such as cellulose and chitin and virulence factors associated with diseases of animals and humans. Secreted proteins have conserved C-terminal domains (CTDs) required for secretion. Cells can be engineered to secrete a foreign protein by attachment of such a CTD. Deletion of genes encoding T9SS components results in defects in motility, adhesion, virulence, polymer digestion, and other processes that require the secreted proteins. Bacteroidetes polysaccharide utilization often involves cell-surface proteins that bind the substrates and perform initial digestion. Long oligosaccharides are then imported across the outer membrane where further hydrolysis takes place. These and other novel features of the Bacteroidetes make this a fertile phylum for molecular exploration.
    All seminars
  • Friday June 1 at 11h: Olve Peersen, Colorado State University, USA. "Structure and Fidelity Modulation of Viral RNA-dependent RNA Polymerases"

    Abstract (...)

    Abstract Positive strand RNA viruses replicate using a virally encoded RNA-dependent RNA polymerase that is responsible for both plus and minus strand RNA synthesis, using one to template the other. Our structural work with picornaviral polymerases elongation complexes have revealed that these enzymes carry out catalysis via the canonical two-metal ion polymerase mechanism, but they close their active site by a unique movement within the palm domain instead of a swinging motion within the fingers. A comprehensive comparison of polymerase structures shows this to be a universal feature of positive strand RNA virus polymerases, and structure-based mutagenesis reveals that this palm domain based movement can be used to evolutionarily fine tune replication fidelity, virus growth. and pathogenesis. Conversely, we are using protein engineering to alter polymerase fidelity and attenuate virus growth as an approach for developing live-attenuated vaccines.
    All seminars
News
  • In February, INSB highlighted the work of Philippe Leone and his colleagues on the type IX secretion system
    See here
  • The AFMB lab, via Isabelle Imbert and François Ferron, spotlighted by the INSB dept of the CNRS in December
    See here
Positions Available


AFMB - UMR7257 CNRS - Aix-Marseille Univ. - Case 932
163 Avenue de Luminy 13288 Marseille CEDEX 09 FRANCE


Latest Publications

© AFMB UMR7257  W3C validation