Changes in the hydrophobic network of the FliGMC domain induce rotational switching of the flagellar motor

• Published in: iScience 2023-08, Vol.26 (8), p.107320-107320, Article 107320
• Main Authors: Nishikino, Tatsuro, Hijikata, Atsushi, Kojima, Seiji, Shirai, Tsuyoshi, Kainosho, Masatsune, Homma, Michio, Miyanoiri, Yohei
• Format: Article
• Language: English
• Subjects: Cell biology; Functional aspects of cell biology; Specialized functions of cells
• ISSN: 2589-0042; 2589-0042
• DOI: 10.1016/j.isci.2023.107320

The FliG protein plays a pivotal role in switching the rotational direction of the flagellar motor between clockwise and counterclockwise. Although we previously showed that mutations in the Gly-Gly linker of FliG induce a defect in switching rotational direction, the detailed molecular mechanism was not elucidated. Here, we studied the structural changes in the FliG fragment containing the middle and C-terminal regions, named FliGMC, and the switch-defective FliGMC-G215A, using nuclear magnetic resonance (NMR) and molecular dynamics simulations. NMR analysis revealed multiple conformations of FliGMC, and the exchange process between these conformations was suppressed by the G215A residue substitution. Furthermore, changes in the intradomain orientation of FliG were induced by changes in hydrophobic interaction networks throughout FliG. Our finding applies to FliG in a ring complex in the flagellar basal body, and clarifies the switching mechanism of the flagellar motor. [Display omitted] •FliG protein determines the rotational direction of the flagellar motor•The structural changes in FliGMC and FliGMC-G215A were studied using NMR•G215A mutation suppressed the exchange process among multiple FliGMC conformations•Hydrophobic interaction networks induced intradomain orientation changes in FliG Cell biology; Specialized functions of cells; Functional aspects of cell biology