A hook to understand motility

Abstract

Structural Biology Bacterial flagella provide the motility required for pathogenicity and biofilm formation. Flagella comprise a motor anchored in the cell membrane, a filament propeller, and a hook region that transmits torque between the motor and the filament. Shibata et al. resolved the complete structure of the hook from Salmonella enterica by cryo–electron microscopy at 2.9-angstrom resolution without imposing helical symmetry. The single protein forms a supercoiled tubular helix composed of 11 protofilaments. Although the hook is built from a single protein, subunits in each protofilament have a slightly different conformation because angles between the three domains are gradually adjusted by interdomain interactions. The conformational tweaks form a curved hook that can rotate by dynamic switching between states. A companion piece by Egelman further discusses the work. Nat. Struct. Mol. Biol. 26 , 941, 848 (2019).