Regensburg 2004 – scientific programme
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SYLS: Life Sciences on the Nanometer Scale - Physics Meets Biology
SYLS 3: Symposium "Life Sciences on the Nanometer Scale - Physics Meets Biology"
SYLS 3.26: Poster
Wednesday, March 10, 2004, 16:00–18:30, B
Picosecond dynamics of bacterial porins investigated by quasi-elastic neutron scattering — •Marie Plazanet1, Cecile Bon2, Franck Gabel3, Sylviane Julien2, Peter Timmins1, and Guiseppe Zaccai3 — 1Institut Laue Langevin, 6 rue Jules Horowitz, 38042 Grenoble Cedex 9, France — 2CNRS/IPBS, 205 route de Narbonnes, 31077 Toulouse cedex, France — 3IBS, 41, rue Jules Horowitz, 38027 Grenoble Cedex 1, France
The survival of bacteria requires a continuous exchange of molecules across the cell wall. Porins, a large class of membrane proteins, are involved in the transport of small hydrophilic molecules across the outer membrane. Porins have peculiar structural features; they fold in a multistranded, closed beta-sheet, exposed to the hydrophobic membrane core on one side and an aqueous channel on the other. Dynamics of these extremely stable proteins clearly modulate the pore activity (i.e. biological activity of the porin), and there is good evidence that this dynamics is modulated by the dynamics of the lipids surrounding the porins.
Experiments have been undertaken on outer membrane fractions of E.Coli, with the natural asymmetric lipid distribution (lipopolysaccharides in the outer leaflet and various phospholipids in the inner leaflet). Samples enriched in porins and samples depleted in porins have been investigated to probe both lipid and porin contribution. While data are still under study, preliminary results show that both systems clearly exhibit very different dynamics on the pico-second timescale. A brief comparison with corresponding results on the bacteriorhodospsin, a representative of the membrane proteins folded in an helix-bundle, will be done.