Table S1.

Data collection and map processing parameters

Data collection and image processing stepsInstrument/software/settingsSpecifics
Cryo-specimen freezingLeica EM GPOne blot; 90% RH; blot time, 2∼3 s
Electron microscopeJEM3200FSC300 KeV, in-column energy filter (25 eV)
DetectorGatan K2 Summit4K × 4K, 5 µm pixel size
Sampling interval0.615 Å/PixelSuperresolution
Exposure rate on specimen5 e2/s5 frames/s
Exposure time10 sTotal dose, 50 e2
Movie-mode micrographs260 used for processingOut of 324 collected
Defocus range0.7–2.5 µm
Defocus determinationEMAN2.1
Particles pickedEMAN2.137,367 for the final map reconstruction
Particle box size240 × 240
Drift and damage
Initial map generationEMAN2.1
Map refinementRELION1.4
Resolution3.5 ÅGold standard FSC at 0.143
ModelingChimera, Coot, and PhenixInitial model 1SS8