Abstract
Bacteria swim and swarm by rotating the micrometers long, helical filaments of their flagella. They change direction by reversing their flagellar rotation, which switches the handedness of the filament’s supercoil. So far, all studied functional filaments are composed of a mixture of L- and R-state flagellin monomers. Here we show in a study of the wild type Firmicute Kurthia sp., that curved, functional filaments can adopt a conformation in vivo that is closely related to a uniform, all-L-state. This sheds additional light on transitions of the flagellar supercoil and uniquely reveals the atomic structure of a wild-type flagellar filament in vivo, including six residues showing clearly densities of O-linked glycosylation.
Highlights
In addition to its crucial role in motility[1], bacterial flagella play a key role in adhesion, biofilm formation, host recognition, and invasion[2]
The 11 flagellar protofilaments twist into a supercoil that can vary in rise and handedness, a phenomenon termed polymorphism[8,9,10]
When we examined curved, fully functional, wild-type flagella from Kurthia sp. strain 11kri[321], we found its flagellin monomers allowed inferring their structure to 2.8 Å resolution
Summary
In addition to its crucial role in motility[1], bacterial flagella play a key role in adhesion, biofilm formation, host recognition, and invasion[2]. It has been predicted that up to 10 different supercoiled conformations may exist, with the two extreme all-L or all-R states resulting in straight, non-functional filaments[12]. The presence of both L- and R-flagellin protofilaments breaks the local, short-range helical symmetry of the flagellar filament, preventing structure determination at high resolution.
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