The flagellar filament is a tublar bundle of 11 proto-filaments, each of which is an axial array of flagellin subunits. A flagellin molecule is composed of 4domains, D0-D3.
Ribon model of F41.
Computer simulation of the protofilament extension.
Three axially aligned F41 molecules were used as a model protofilament. The top molecule was fixed and the bottom one was pulled down by 0.1Å at every step and the deformation of the middle molecules was examined through energy minimization. At certain extension, an abrupt conformational jump took place at the beta-hairpin structure of domain D1. The downward shift of the beta-hairpin appears to work as a mechanical switch to change the repeat distance of the protofilaments.
