PT  - JOURNAL ARTICLE
AU  - Terahara, Naoya
AU  - Kodera, Noriyuki
AU  - Uchihashi, Takayuki
AU  - Ando, Toshio
AU  - Namba, Keiichi
AU  - Minamino, Tohru
TI  - Na<sup>+</sup>-induced structural transition of MotPS for stator assembly of the <em>Bacillus</em> flagellar motor
AID  - 10.1126/sciadv.aao4119
DP  - 2017 Nov 01
TA  - Science Advances
PG  - eaao4119
VI  - 3
IP  - 11
4099  - http://advances.sciencemag.org/content/3/11/eaao4119.short
4100  - http://advances.sciencemag.org/content/3/11/eaao4119.full
SO  - Sci Adv2017 Nov 01; 3
AB  - The bacterial flagellar motor consists of a rotor and a dozen stator units and regulates the number of active stator units around the rotor in response to changes in the environment. The MotPS complex is a Na+-type stator unit in the Bacillus subtilis flagellar motor and binds to the peptidoglycan layer through the peptidoglycan-binding (PGB) domain of MotS to act as the stator. The MotPS complex is activated in response to an increase in the Na+ concentration in the environment, but the mechanism of this activation has remained unknown. We report that activation occurs by a Na+-induced folding and dimer formation of the PGB domain of MotS, as revealed in real-time imaging by high-speed atomic force microscopy. The MotPS complex showed two distinct ellipsoid domains connected by a flexible linker. A smaller domain, corresponding to the PGB domain, became structured and unstructured in the presence and absence of 150 mM NaCl, respectively. When the amino-terminal portion of the PGB domain adopted a partially stretched conformation in the presence of NaCl, the center-to-center distance between these two domains increased by up to 5 nm, allowing the PGB domain to reach and bind to the peptidoglycan layer. We propose that assembly of the MotPS complex into a motor proceeds by means of Na+-induced structural transitions of its PGB domain.