title: Sodium-driven energy conversion for flagellar rotation of the earliest divergent hyperthermophilic bacterium.
abstract: Aquifex aeolicus is a hyperthermophilic, hydrogen-oxidizing and carbon-fixing bacterium that can grow at temperatures up to 95 °C. A. aeolicus has an almost complete set of flagellar genes that are conserved in bacteria. Here we observed that A. aeolicus has polar flagellum and can swim with a speed of 90 μm s(-1) at 85 °C. We expressed the A. aeolicus mot genes (motA and motB), which encode the torque generating stator proteins of the flagellar motor, in a corresponding mot nonmotile mutant of Escherichia coli. Its motility was slightly recovered by expression of A. aeolicus MotA and chimeric MotB whose periplasmic region was replaced with that of E. coli. A point mutation in the A. aeolicus MotA cytoplasmic region remarkably enhanced the motility. Using this system in E. coli, we demonstrate that the A. aeolicus motor is driven by Na(+). As motor proteins from hyperthermophilic bacteria represent the earliest motor proteins in evolution, this study strongly suggests that ancient bacteria used Na(+) for energy coupling of the flagellar motor. The Na(+)-driven flagellar genes might have been laterally transferred from early-branched bacteria into late-branched bacteria and the interaction surfaces of the stator and rotor seem not to change in evolution.
authors.affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Takekawa
authors.affiliation: The HAKUBI Center for Advanced Research/Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Nishiyama
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Kaneseki
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Kanai
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.
authors.forename: Haruyuki
authors.initials: H
authors.lastname: Atomi
authors.affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Kojima
authors.affiliation: Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
authors.forename: Michio
authors.initials: M
authors.lastname: Homma
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004734:Energy Metabolism / Q000502:physiology*; D019143:Evolution, Molecular; D005407:Flagella / Q000235:genetics / Q000378:metabolism*; D012399:Rotation; D012964:Sodium / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C063010:MotA protein, Bacteria; C064779:MotB protein, Bacteria; D012964:Sodium