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Nature 410, 331-337 (15 March 2001) | doi:10.1038/35066504; Received 2 November 2000; Accepted 11 January 2001

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Structure of the bacterial flagellar protofilament and implications for a switch for supercoiling

Fadel A. Samatey1, Katsumi Imada1, Shigehiro Nagashima1, Ferenc Vonderviszt2, Takashi Kumasaka3, Masaki Yamamoto3 & Keiichi Namba1,4

  1. Protonic NanoMachine Project, ERATO, JST, 3-4 Hikaridai, Seika, Kyoto 619-0237, Japan
  2. Department of Physics, University of Veszprém, Egyetem, u.10 H-8201, Hungary
  3. RIKEN Harima Institute, 1-1-1 Kouto, Mikazuki, Hyogo 679-5198, Japan
  4. Advanced Technology Research Laboratories, Matsushita Electric Industrial Co., Ltd, 3-4 Hikaridai, Seika, Kyoto 619-0237, Japan

Correspondence to: Keiichi Namba1,4 Correspondence and requests for materials should be addressed to K.N. (e-mail: Email: keiichi@crl.mei.co.jp). Atomic coordinates have been deposited in the Protein Data Bank under accession code 1IO1.

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The bacterial flagellar filament is a helical propeller constructed from 11 protofilaments of a single protein, flagellin. The filament switches between left- and right-handed supercoiled forms when bacteria switch their swimming mode between running and tumbling. Supercoiling is produced by two different packing interactions of flagellin called L and R. In switching from L to R, the intersubunit distance (approx52 Å) along the protofilament decreases by 0.8 Å. Changes in the number of L and R protofilaments govern supercoiling of the filament. Here we report the 2.0 Å resolution crystal structure of a Salmonella flagellin fragment of relative molecular mass 41,300. The crystal contains pairs of antiparallel straight protofilaments with the R-type repeat. By simulated extension of the protofilament model, we have identified possible switch regions responsible for the bi-stable mechanical switch that generates the 0.8 Å difference in repeat distance.

  1. Protonic NanoMachine Project, ERATO, JST, 3-4 Hikaridai, Seika, Kyoto 619-0237, Japan
  2. Department of Physics, University of Veszprém, Egyetem, u.10 H-8201, Hungary
  3. RIKEN Harima Institute, 1-1-1 Kouto, Mikazuki, Hyogo 679-5198, Japan
  4. Advanced Technology Research Laboratories, Matsushita Electric Industrial Co., Ltd, 3-4 Hikaridai, Seika, Kyoto 619-0237, Japan

Correspondence to: Keiichi Namba1,4 Correspondence and requests for materials should be addressed to K.N. (e-mail: Email: keiichi@crl.mei.co.jp). Atomic coordinates have been deposited in the Protein Data Bank under accession code 1IO1.