Fig. 3: Cryo-EM analysis of the whole apparatus.

a Top: side view of the 3D cryo-EM maps determined separately for three variants of the mechanism, with the shaft docked to the stator unit 1, 2, or 3, respectively. See Supplementary Figs. 12–14. Bottom: cross-sectional slices through the maps. Red, blue, and yellow arrows highlight the asymmetric feature of the stator, the T-crossbar, and the cam, respectively. b 2D class averages of the mechanism with the shaft bound to stator unit 1. Blue and yellow arrows highlight crossbar and cam of the shaft, respectively. Scale bar: 50 nm. c 2D class averages of the mechanism determined from a sample where the shaft was released from the docking site. Blue and yellow arrows point to where crossbar and cam would be expected to be located, but the features are blurred. Scale bar: 50 nm. d Top: side views of three representative 3D classes discovered in the cryo-EM micrograph data determined from the same sample with the released camshaft. Bottom: cross-sectional slices through the 3D classes. Red arrows indicate the asymmetric feature of the stator, blue arrows show the position of the camshaft T-crossbar. The cam could not be resolved in the data. See Supplementary Fig. 15. e Overlay of frames from movies from multibody refinement analysis of data acquired separately, with the shaft docked to one stator unit 1, 2 or 3, respectively. Black arrows indicate the observed range of rotary motion of the shaft relative to the stator. f As in e, but for the sample where the shaft was released from its docking site. Scale bars of all 3D maps: 10 nm.