Physicochemical Evidence that Francisella FupA and FupB Proteins Are Porins

International Journal of Molecular Sciences

Corinne Mercier¹  DonaldK. Martin²  Beatrice Schaack³  Patricia Renesto³  Claire Siebert³ 

[1] GEM Team, TIMC-IMAG, CNRS, INP, Université Grenoble Alpes, 38000 Grenoble, France;SyNaBi Team, TIMC-IMAG, CNRS, INP, Université Grenoble Alpes, 38000 Grenoble, France;TheRex Team, TIMC-IMAG, CNRS, INP, Université Grenoble Alpes, 38000 Grenoble, France;

关键词: Francisella tularensis;    FupA;    FupB;    porins;    fluorescence flux;    impedance spectroscopy;   

DOI  :  10.3390/ijms21155496

来源: DOAJ

【 摘 要 】

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.

【 授权许可】

Unknown