Graduate School of Frontier Biosciences, Osaka University


The tetrameric MotA complex as the core of the flagellar motor stator from hyperthermophilic bacterium

Journal Sci Rep 6, 31526 (2016)
Authors Norihiro Takekawa (1), Naoya Terahara (2), Takayuki Kato (2), Mizuki Gohara (1), Kouta Mayanagi (3), Atsushi Hijikata (4), Yasuhiro Onoue (1), Seiji Kojima (1), Tsuyoshi Shirai (4), Keiichi Namba (2), Michio Homma (1)
  1. Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
  2. Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
  3. Medical Institute of Bioregulation, Kyushu University, Higashi-ku, Fukuoka 812-8581, Japan; JST, PRESTO, Fukuoka 812-8582, Japan
  4. Department of Bioscience, Nagahama Institute of BioScience and Technology, 1266 Tamura, Nagahama, 526-0829, Japan
Title The tetrameric MotA complex as the core of the flagellar motor stator from hyperthermophilic bacterium
PubMed 27531865
Laboratory Protonic NanoMachine Group 〈Prof. Namba〉
Abstract Rotation of bacterial flagellar motor is driven by the interaction between the stator and rotor, and the driving energy is supplied by ion influx through the stator channel. The stator is composed of the MotA and MotB proteins, which form a hetero-hexameric complex with a stoichiometry of four MotA and two MotB molecules. MotA and MotB are four- and single-transmembrane proteins, respectively. To generate torque, the MotA/MotB stator unit changes its conformation in response to the ion influx, and interacts with the rotor protein FliG. Here, we overproduced and purified MotA of the hyperthermophilic bacterium Aquifex aeolicus. A chemical crosslinking experiment revealed that MotA formed a multimeric complex, most likely a tetramer. The three-dimensional structure of the purified MotA, reconstructed by electron microscopy single particle imaging, consisted of a slightly elongated globular domain and a pair of arch-like domains with spiky projections, likely to correspond to the transmembrane and cytoplasmic domains, respectively. We show that MotA molecules can form a stable tetrameric complex without MotB, and for the first time, demonstrate the cytoplasmic structure of the stator.