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Structure of the C-terminal domain of FliG, a component of the rotor in the bacterial flagellar motor

Nature volume 400, pages 472–475 (1999)Cite this article

Abstract

Many motile species of bacteria are propelled by flagella, which are rigid helical filaments turned by rotary motors in the cell membrane1,2,3. The motors are powered by the transmembrane gradient of protons or sodium ions. Although bacterial flagella contain many proteins, only three—MotA, MotB and FliG—participate closely in torque generation. MotA and MotB are ion-conducting membrane proteins that form the stator of the motor. FliG is a component of the rotor, present in about 25 copies per flagellum. It is composed of an amino-terminal domain that functions in flagellar assembly and a carboxy-terminal domain (FliG-C) that functions specifically in motor rotation. Here we report the crystal structure of FliG-C from the hyperthermophilic eubacterium Thermotoga maritima. Charged residues that are important for function, and which interact with the stator protein MotA4,5, cluster along a prominent ridge on FliG-C. On the basis of the disposition of these residues, we present a hypothesis for the orientation of FliG-C domains in the flagellar motor, and propose a structural model for the part of the rotor that interacts with the stator.

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Figure 1: Alignment of E.coli and T. maritima FliG-C protein sequences.
Figure 2: Stereoview ribbon representation of the FliG-C structure.
Figure 3: Stereoview of the putative active-site ridge of FliG-C.
Figure 4: Hypothesis for the location and orientation of FliG-C in the flagellar motor.

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Acknowledgements

We thank H. Bellamy, A. Kolatkar, M. Mathews, J. R. Knowlton and J. D. Phillips for assistance with data collection, and R. Huber for T. maritima genomic DNA. Preliminary sequence data were obtained from The Institute for Genomic Research website at http://www.tigr.org. Sequencing of T.maritima was accomplished with support from the US Department of Energy (DoE). The SSRL Biotechnology Program is supported by the US National Institutes of Health (NIH), National Center for Research Resources, Biomedical Technology Program, and by the DoE Office of Biological and Enivronmental Research. Use of APS was supported by the DoE Basic Energy Sciences, Office of Science. Use of the BioCARS Sector 14 was supported by the NIH National Center for Research Resources. S.A.L. was partially supported by an NIH training grant. Supported by grants from the NSF (to D.F.B.) and NIH (to C.P.H.).

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  1. Scott A. Lloyd and Frank G. Whitby: These authors contributed equally to this work

Authors and Affiliations

  1. Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, 84112-0840, Utah, USA

    Scott A. Lloyd & David F. Blair

  2. Department of Biochemistry, University of Utah, 50 North Medical Drive, Salt Lake City, 84132, Utah, USA

    Frank G. Whitby & Christopher P. Hill

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Correspondence to David F. Blair or Christopher P. Hill.

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Lloyd, S., Whitby, F., Blair, D. et al. Structure of the C-terminal domain of FliG, a component of the rotor in the bacterial flagellar motor. Nature 400, 472–475 (1999). https://doi.org/10.1038/22794

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