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Article

Physicochemical Evidence that Francisella FupA and FupB Proteins Are Porins

1
TheRex Team, TIMC-IMAG, CNRS, INP, Université Grenoble Alpes, 38000 Grenoble, France
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GEM Team, TIMC-IMAG, CNRS, INP, Université Grenoble Alpes, 38000 Grenoble, France
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SyNaBi Team, TIMC-IMAG, CNRS, INP, Université Grenoble Alpes, 38000 Grenoble, France
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CEA, IBS, CNRS, Université Grenoble Alpes, 38044 Grenoble, France
*
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2020, 21(15), 5496; https://doi.org/10.3390/ijms21155496
Received: 11 July 2020 / Revised: 25 July 2020 / Accepted: 28 July 2020 / Published: 31 July 2020
Responsible for tularemia, Francisella tularensis bacteria are highly infectious Gram-negative, category A bioterrorism agents. The molecular mechanisms for their virulence and resistance to antibiotics remain largely unknown. FupA (Fer Utilization Protein), a protein mediating high-affinity transport of ferrous iron across the outer membrane, is associated with both. Recent studies demonstrated that fupA deletion contributed to lower F. tularensis susceptibility towards fluoroquinolones, by increasing the production of outer membrane vesicles. Although the paralogous FupB protein lacks such activity, iron transport capacity and a role in membrane stability were reported for the FupA/B chimera, a protein found in some F. tularensis strains, including the live vaccine strain (LVS). To investigate the mode of action of these proteins, we purified recombinant FupA, FupB and FupA/B proteins expressed in Escherichia coli and incorporated them into mixed lipid bilayers. We examined the porin-forming activity of the FupA/B proteoliposomes using a fluorescent 8-aminonaphthalene-1,3,6-trisulfonic acid, disodium salt (ANTS) probe. Using electrophysiology on tethered bilayer lipid membranes, we confirmed that the FupA/B fusion protein exhibits pore-forming activity with large ionic conductance, a property shared with both FupA and FupB. This demonstration opens up new avenues for identifying functional genes, and novel therapeutic strategies against F. tularensis infections. View Full-Text
Keywords: Francisella tularensis; FupA; FupB; porins; fluorescence flux; impedance spectroscopy Francisella tularensis; FupA; FupB; porins; fluorescence flux; impedance spectroscopy
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MDPI and ACS Style

Siebert, C.; Mercier, C.; Martin, D.K.; Renesto, P.; Schaack, B. Physicochemical Evidence that Francisella FupA and FupB Proteins Are Porins. Int. J. Mol. Sci. 2020, 21, 5496. https://doi.org/10.3390/ijms21155496

AMA Style

Siebert C, Mercier C, Martin DK, Renesto P, Schaack B. Physicochemical Evidence that Francisella FupA and FupB Proteins Are Porins. International Journal of Molecular Sciences. 2020; 21(15):5496. https://doi.org/10.3390/ijms21155496

Chicago/Turabian Style

Siebert, Claire, Corinne Mercier, Donald K. Martin, Patricia Renesto, and Beatrice Schaack. 2020. "Physicochemical Evidence that Francisella FupA and FupB Proteins Are Porins" International Journal of Molecular Sciences 21, no. 15: 5496. https://doi.org/10.3390/ijms21155496

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