Carcinogenic bacterium Helicobacter pylori uses the flagellar motor to drill into the mucus layer of the stomach and move towards the epithelial surface. Flagellar rotation is powered by the proton influx through the stator ring MotA/MotB. The work presented at the meeting will inform the audience about the latest discoveries of novel factors that mediate stator/rotor interaction and our latest findings that establish the relationship between the structure, dynamics and function of MotB. We have determined the first crystal structure of the protein domain that anchors the proton-motive-force-generating mechanism of the bacterial flagellar motor to the cell wall, and formulated a model of how the stator attaches to peptidoglycan (PG). Analysis of the accumulated structural, biochemical and mutagenesis data suggested a mechanism by which MotB’s cell wall binding activity is inhibited until the stator is incorporated into the motor. Putting this in the perspective of the stator assembly and activation, we propose that in the pre-assembled stator units with the closed channel the linker is partially folded, stabilizing the dimer in the conformation that cannot insert into the PG mesh. This inhibition occurs via a dual mechanism: distance constraint and suboptimal geometry of two PG-binding sites. When the diffusing stator unit collides with the rotor, a drastic conformational change in MotB is induced, resulting in unwinding of the two beta strands at the edge of the beta sheet, extension of the linker, re-arrangement of the dimer geometry and insertion of the Pal-like conserved core domain into PG mesh. Implications for stator activation via rotational displacement of the transmembrane helices of MotB will be discussed.

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