3AJC

Structure of the MC domain of FliG (PEV), a CW-biased mutant

3AJC の概要

• エントリーDOI: 10.2210/pdb3ajc/pdb
• 分子名称: Flagellar motor switch protein fliG (2 entities in total)
• 機能のキーワード: chemotaxis, flagellum, flagellar motor, structural protein
• 由来する生物種: Thermotoga maritima
• 細胞内の位置: Cell inner membrane; Peripheral membrane protein; Cytoplasmic side (By similarity): Q9WY63
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 26047.17

構造登録者

Imada, K.,Minamino, T.,Kinoshita, M.,Namba, K. (登録日: 2010-05-27, 公開日: 2011-05-11, 最終更新日: 2024-03-13)

主引用文献

Minamino, T.,Imada, K.,Kinoshita, M.,Nakamura, S.,Morimoto, Y.V.,Namba, K.
Structural insight into the rotational switching mechanism of the bacterial flagellar motor
Plos Biol., 9:e1000616-e1000616, 2011

PubMed Abstract: The bacterial flagellar motor can rotate either clockwise (CW) or counterclockwise (CCW). Three flagellar proteins, FliG, FliM, and FliN, are required for rapid switching between the CW and CCW directions. Switching is achieved by a conformational change in FliG induced by the binding of a chemotaxis signaling protein, phospho-CheY, to FliM and FliN. FliG consists of three domains, FliG(N), FliG(M), and FliG(C), and forms a ring on the cytoplasmic face of the MS ring of the flagellar basal body. Crystal structures have been reported for the FliG(MC) domains of Thermotoga maritima, which consist of the FliG(M) and FliG(C) domains and a helix E that connects these two domains, and full-length FliG of Aquifex aeolicus. However, the basis for the switching mechanism is based only on previously obtained genetic data and is hence rather indirect. We characterized a CW-biased mutant (fliG(ΔPAA)) of Salmonella enterica by direct observation of rotation of a single motor at high temporal and spatial resolution. We also determined the crystal structure of the FliG(MC) domains of an equivalent deletion mutant variant of T. maritima (fliG(ΔPEV)). The FliG(ΔPAA) motor produced torque at wild-type levels under a wide range of external load conditions. The wild-type motors rotated exclusively in the CCW direction under our experimental conditions, whereas the mutant motors rotated only in the CW direction. This result suggests that wild-type FliG is more stable in the CCW state than in the CW state, whereas FliG(ΔPAA) is more stable in the CW state than in the CCW state. The structure of the TM-FliG(MC)(ΔPEV) revealed that extremely CW-biased rotation was caused by a conformational change in helix E. Although the arrangement of FliG(C) relative to FliG(M) in a single molecule was different among the three crystals, a conserved FliG(M)-FliG(C) unit was observed in all three of them. We suggest that the conserved FliG(M)-FliG(C) unit is the basic functional element in the rotor ring and that the PAA deletion induces a conformational change in a hinge-loop between FliG(M) and helix E to achieve the CW state of the FliG ring. We also propose a novel model for the arrangement of FliG subunits within the motor. The model is in agreement with the previous mutational and cross-linking experiments and explains the cooperative switching mechanism of the flagellar motor.

PubMed: 21572987
DOI: 10.1371/journal.pbio.1000616

実験手法

X-RAY DIFFRACTION (2.3 Å)