Changes in the hydrophobic network of the FliGMC domain induce rotational switching of the flagellar motor
Tatsuro Nishikino,
Atsushi Hijikata,
Seiji Kojima,
Tsuyoshi Shirai,
Masatsune Kainosho,
Michio Homma,
Yohei Miyanoiri
Affiliations
Tatsuro Nishikino
Laboratory for Ultra-High Magnetic Field NMR Spectroscopy, Research Center for Next-Generation Protein Sciences, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
Atsushi Hijikata
Department of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura, Nagahama, Shiga 526-0829, Japan
Seiji Kojima
Division of Biological Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
Tsuyoshi Shirai
Department of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura, Nagahama, Shiga 526-0829, Japan
Masatsune Kainosho
Graduate School of Pharmaceutical Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan; Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan
Michio Homma
Division of Biological Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan; Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan; Corresponding author
Yohei Miyanoiri
Laboratory for Ultra-High Magnetic Field NMR Spectroscopy, Research Center for Next-Generation Protein Sciences, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan; Graduate School of Pharmaceutical Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan; Corresponding author
Summary: 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.
