Dynamic interplay of membrane‐proximal POTRA domain and conserved loop L6 in Omp85 transporter FhaC |
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| Authors: | Jeremy Guérin Nathalie Saint Catherine Baud Albano C Meli Emilien Etienne Camille Locht Hervé Vezin Françoise Jacob‐Dubuisson |
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| Affiliation: | 1. Institut Pasteur de Lille, Lille Cedex, France;2. Université de Lille, Lille, France;3. CNRS UMR 8204, Lille, France;4. INSERM U1019, Lille, France;5. PhyMedExp, University of Montpellier, 34295, Montpellier cedex 05, France;6. Aix‐Marseille Université, Marseille cedex 20, France;7. CNRS UMR8516, Villeneuve d'Ascq, France |
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| Abstract: | Omp85 transporters mediate protein insertion into, or translocation across, membranes. They have a conserved architecture, with POTRA domains that interact with substrate proteins, a 16‐stranded transmembrane β barrel, and an extracellular loop, L6, folded back in the barrel pore. Here using electrophysiology, in vivo biochemical approaches and electron paramagnetic resonance, we show that the L6 loop of the Omp85 transporter FhaC changes conformation and modulates channel opening. Those conformational changes involve breaking the conserved interaction between the tip of L6 and the inner β‐barrel wall. The membrane‐proximal POTRA domain also exchanges between several conformations, and the binding of FHA displaces this equilibrium. We further demonstrate a dynamic, physical communication between the POTRA domains and L6, which must take place via the β barrel. Our findings thus link all three essential components of Omp85 transporters and indicate that they operate in a concerted fashion in the transport cycle. |
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