Fig. 1: Essential role of FlhF’s B-domain in interacting with FliG.

a Scheme of the architecture of the bacterial flagellum. b Schematic representation of S. putrefaciens FlhF’s domain structure. c Scheme of the flagellation of the Gram-negative model organism S. putrefaciens featuring one polar and one lateral flagellum, whose localization is dependent and independent of FlhF, respectively. The subpolar position of the flagellum is indicated in dashed gray. d Upper panel: FlhF interacts with FliG in the yeast two-hybrid (Y2H) assay, while showing no interaction with FliF-C, FliM, and FliN from the polar system. Lower panel: FlhF exclusively associates with FliG from the polar flagellar system but not with FliG from the lateral system. e Upper panel: The B-domain of FlhF is sufficient to interact with FliG, while no interaction is observed with FliF-C, FliM, and FliN of the polar system. Lower panel: The B-domain of FlhF demonstrates its ability to differentiate between the FliG proteins of the polar and lateral systems in the Y2H. For Fig. 1d, e: The growth of cells, co-expressing the FlhF and FlhF-B bait proteins and the indicated prey proteins, was assessed on SC-Leu-Trp (-LT), SC-His-Leu-Trp (-HLT; HIS3 reporter) and SC-Ade-Leu-Trp (-ALT; ADE2 reporter) plates. The reporter strain PJ69-4A was used in which the HIS3 and ADE2 reporter genes are under the transcriptional control of the GAL1 and GAL2 promoter, respectively.