Extended Data Fig. 1: Workflow for the cryo-EM structure determination of NifEN and NifENX.

a, Representative micrograph and 2D class averages from 14,022 recorded movies. b, 6,835,000 particles were picked for 2D classification and initial 3D reconstruction and subsequently split into two 3D classes representing: c, a NifE₂N₂X from 257k particles and d, a NifE₂N₂ structure from 262k particles. The obtained local resolution was similar for the NifE₂N₂ core but increased for the resolved NifX monomer. e, Angular distribution of particles used for the 3D reconstruction, and f, FSC curves (threshold 0.143) for NifE₂N₂X. g, Angular distribution of particles used for the 3D reconstruction and h, FSC curves (threshold 0.143) for NifE₂N₂.