Build-and-Retrieve (BaR) Pipeline. Integrating cryo-EM with the BaR data processing methodology allows us to obtain atomic-level-resolution protein structures directly from crude preparations straight from their native environment. After sample extraction (A), a total of 13808 raw micrographs were collected using cryo-EM (B). Following the BaR protocol (C), an unbiased selection was applied on 13,002 motion-corrected micrographs to generate 17,985,649 initial particles. The 2D classification was used to generate a subset of a clean particle stack that contains 8,706,530 particles. Classes of particles that contain clear 2D features were used to “build” the low-resolution initial models, which were used to “retrieve” more particles from the clean particle stack. The improved maps at ∼3 Å resolution were used for protein identification (D), and final maps were used for model building and refinement. 2D, 2-dimensional; 3D, 3-dimensional; FSC, Fourier shell correlation; GS-FSC, gold-standard Fourier shell correlation.