Image reconstruction procedure and reconstruction quality. (A) Flowchart summarizing steps taken to process cryo-EM images in order to generate a 3-D reconstruction of F-actin–tropomyosin decorated with human cardiac S1, in which loop-4 residues 366–372 were mutated to glycine. (B) Map-to-model fit of atomic models of filament components to the reconstruction, here focused on five centrally located actin protomers, an associated segment of tropomyosin, and one S1 motor domain. (C) Regions of the fitted reconstruction magnified to indicate the quality of the data showing selected chains within actin and myosin as well as the ADP bound to actin, rendered in ChimeraX. (D) Fourier shell correlation of the split reconstruction data sets, indicating 3.6 Å resolution at a value of 0.143.