a, Structure of the wild-type, octameric enzyme (1POK). b, Structure is rotated along the horizontal axis to show the orientation seen in filaments. c, Representative cryo-electron microscopy image after whole-image motion correction, showing filaments. d, Two-dimensional class averages. e, Final three-dimensional reconstruction. The wild-type structure solved by X-ray crystallography was fitted as a rigid body inside the map, using separate fits for the two tetrameric rings. f, Local resolution map (ResMap) in ångströms. g, Fourier shell correlation for the final reconstruction. The horizontal dotted line indicates the Fourier shell correlation = 0.143 criterion.