Sobe, Richard C.Gilbert, CrystalVo, LamAlexandre, GladysScharf, Birgit E.2024-01-222024-01-222022-07-280950-382Xhttps://hdl.handle.net/10919/117508The bacterial flagellum is a complex macromolecular machine that drives bacteria through diverse fluid environments. Although many components of the flagellar motor are conserved across species, the roles of FliL are numerous and species-specific. Here, we have characterized an additional player required for flagellar motor function in Sinorhizobium meliloti, MotF, which we have identified as a FliL paralog. We performed a comparative analysis of MotF and FliL, identified interaction partners through bacterial two-hybrid and pull-down assays, and investigated their roles in motility and motor rotation. Both proteins form homooligomers, and interact with each other, and with the stator proteins MotA and MotB. The ∆motF mutant exhibits normal flagellation but its swimming behavior and flagellar motor activity are severely impaired and erratic. In contrast, the ∆fliL mutant is mostly aflagellate and nonmotile. Amino acid substitutions in cytoplasmic regions of MotA or disruption of the proton channel plug of MotB partially restored motor activity to the ∆motF but not the ∆fliL mutant. Altogether, our findings indicate that both, MotF and FliL, are essential for flagellar motor torque generation in S. meliloti. FliL may serve as a scaffold for stator integration into the motor, and MotF is required for proton channel modulation.Pages 223-24321 page(s)application/pdfenCreative Commons Attribution-NonCommercial-NoDerivatives 4.0 Internationalchemotaxisflagellar-basal bodyproton channel plugswimming motilitytorque generationFlagellaSinorhizobium melilotiProtonsBacterial ProteinsTorqueMolecular Motor ProteinsArticle - Refereedhttps://doi.org/10.1111/mmi.149641183Scharf, Birgit [0000-0001-6271-8972]358088931365-2958