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Dynamic interplay of membrane‐proximal POTRA domain and conserved loop L 6 in O mp85 transporter FhaC
Author(s) -
Guérin Jeremy,
Saint Nathalie,
Baud Catherine,
Meli Albano C.,
Etienne Emilien,
Locht Camille,
Vezin Hervé,
JacobDubuisson Françoise
Publication year - 2015
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.13137
Subject(s) - biology , biophysics , transporter , loop (graph theory) , transmembrane domain , transmembrane protein , barrel (horology) , extracellular , membrane , transport protein , bacterial outer membrane , microbiology and biotechnology , biochemistry , receptor , materials science , escherichia coli , mathematics , combinatorics , composite material , gene
Summary 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, L 6, folded back in the barrel pore. Here using electrophysiology, in vivo biochemical approaches and electron paramagnetic resonance, we show that the L 6 loop of the O mp85 transporter FhaC changes conformation and modulates channel opening. Those conformational changes involve breaking the conserved interaction between the tip of L 6 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 L 6, which must take place via the β barrel. Our findings thus link all three essential components of O mp85 transporters and indicate that they operate in a concerted fashion in the transport cycle.