期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 110, 期 15, 页码 6133-6138出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1222655110
关键词
X-ray crystallography; molecular motor
资金
- Ministry of Education, Science, and Culture of Japan [18074006, 23115008]
- Japan Science and Technology Corporation [23247024, 24657087]
- Japan Society for the Promotion of Science
- Grants-in-Aid for Scientific Research [18074006, 24657087] Funding Source: KAKEN
Flagellar motility is a key factor for bacterial survival and growth in fluctuating environments. The polar flagellum of a marine bacterium, Vibrio alginolyticus, is driven by sodium ion influx and rotates approximately six times faster than the proton-driven motor of Escherichia coli. The basal body of the sodium motor has two unique ring structures, the T ring and the H ring. These structures are essential for proper assembly of the stator unit into the basal body and to stabilize the motor. FlgT, which is a flagellar protein specific for Vibrio sp., is required to form and stabilize both ring structures. Here, we report the crystal structure of FlgT at 2.0-angstrom resolution. FlgT is composed of three domains, the N-terminal domain (FlgT-N), the middle domain (FlgT-M), and the C-terminal domain (FlgT-C). FlgT-M is similar to the N-terminal domain of TolB, and FlgT-C resembles the N-terminal domain of Flil and the alpha/beta subunits of F-1-ATPase. To elucidate the role of each domain, we prepared domain deletion mutants of FlgT and analyzed their effects on the basal-body ring formation. The results suggest that FlgT-N contributes to the construction of the H-ring structure, and FlgT-M mediates the T-ring association on the LP ring. FlgT-C is not essential but stabilizes the H-ring structure. On the basis of these results, we propose an assembly mechanism for the basal-body rings and the stator units of the sodium-driven flagellar motor.
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