Particle stack contains images normalized with zero average and constant variance. The particle density is dark on light background. The data were collected on a Falcon II detector mounted on an FEI F30 microscope running at 300 kV. The Frealign parameter file contains the final particle alignments and classification results for the best class that was used to calculate the published 11-Å reconstruction. The table at the end of the parameter file does not contain the final FSC curve; the final FSC curve was calculated using more tightly masked half reconstructions (see related publication).