Graduate School of Frontier Biosciences, Osaka University

Japanese

Complete atomic model of the bacterial flagellar filament by electron cryomicroscopy.

Journal Nature 424, 643-650 (2003)
Authors Yonekura K, Maki-Yonekura S, Namba K.
Title Complete atomic model of the bacterial flagellar filament by electron cryomicroscopy.
PubMed 12904785
Laboratory JEOL YOKOGUSHI Research Alliance Laboratories 〈Prof. Namba〉
Abstract The bacterial flagellar filament is a helical propeller for bacterial locomotion. Electron cryomicroscopy and image analysis visualized its atomic structure and unveiled the precise switching mechanism of this switchable helical propeller at nano-scale.
Description The bacterial flagellar filament is a helical propeller for bacterial locomotion. It is a helical assembly of a single protein, flagellin, and its tubular structure is formed by 11 protofilaments in two distinct conformations, L- and R-type, for supercoiling. The X-ray crystal structure of a flagellin fragment lacking about 100 terminal residues revealed the protofilament structure, but the full filament structure is still essential for understanding the mechanism of supercoiling and polymerization. Here we report a complete atomic model of the R-type filament by electron cryomicroscopy. A density map obtained from image data up to 4 Å resolution shows the feature of -helical backbone and some large side chains. The atomic model built on the map reveals intricate molecular packing and an -helical coiled coil formed by the terminal chains in the inner core of the filament, with its intersubunit hydrophobic interactions having an important role in stabilizing the filament.
BFfilament-100.jpgFigure 1: Computer graphic representation of the assembly process of the bacterial flagellum and a swimming bacterium with a rotating bundle of the helical flagellar filaments behind the cell body. The diameter of the filament is 20 nm and the length is about 10 mm.





Figure2: Ca backbone model of the atomic structure of the flagellar filament. Side views showing the inner side (left) and outer surface (right). The amino acid sequence of each flagellin subunit is color-coded from blue for the N-terminus to red for the C-terminus.


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Moving Images Collection
(JST Website)





A Rotary NanoMachine
~Understanding the Structure and Dynamics of Bacterial Flagella~
Protonic NanoMachine Project, ERATO, Japan Science and Technology Corporation