POSTERS - BLAST X - University of Utah

BLAST X Poster #51
CRYOEM STRUCTURE OF THE HOOK-FILAMENT JUNCTION OF SALMONELLA
Fumiaki Makino (1), Takayuki Kato (1), Keiichi Namba (1)
1: Grad. Sch. of Frontier Biosci., Osaka Univ.
The bacterial flagellum is a biological nanomachine for the locomotion of bacteria. The
flagellum consists of three functional parts: the basal body as a rotary motor, the filaments as a
helical propeller, and the hook as a universal joint that connects the above-mentioned two parts.
The filament is a tubular structure made of a single protein, FliC. It transforms into various
helical forms in response to mechanical perturbation by reversal of motor rotation. The hook is
also a tubular structure made of a single protein, FlgE, but is more flexible than the filament,
allowing it to transmit motor torque to the filament regardless of its orientation. The hookfilament
junction made of two proteins, FlgK and FlgL, connects these two mechanically distinct
structures. It works as a mechanical adapter, allowing the two parts to go through dynamic
conformational changes independently. To understand the adapter mechanism, we have
analyzed the structure of the hook-filament junction by electron cryomicroscopy (cryoEM). We
needed a Salmonella strain that produces short filaments for efficient data collection. We used a
strain, MMC1660, which produces short filament due to a significantly low efficiency of FliC
expression controlled by the addition of tetracycline. We established a procedure to purify the
hook-basal body with short filament, collected cryoEM images and carried out image analysis.
We will show the cryoEM structure of the hook-filament junction complex.
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