Rotational symmetry of the C ring and a mechanism for the flagellar rotarymotor

FliG, FliM, and FliN, key proteins for torque generation, are located in tw o rings. The first protein is in the M ring and the last two are in tbe C r ing, The rotational symmetries of the C and M rings have been determined to be about 34 (this paper) and 26 (previous work), respectively. The mechani sm proposed here depends on the symmetry mismatch between the rings: the C ring extends 34 levers, of which 26 can bind to the 26 equivalent sites on the M ring. The remaining 8 levers bind to proton-pore complexes (studs) to form 8 torque generators. Movement results from the swapping of stud-bound levers with M ring-bound levers. The model predicts that both the M and C rings rotate in the same direction but at different speeds.