The original images that were part of the ensemble map went through a ‘consensus classification’ procedure aimed at separating them into two algorithmically stable classes. Essentially, and as described in more detail in Section 2, we performed two independent classifications, further selecting those particles that were consistently together throughout the two classifications. In this way, we obtained the two new classes shown in Fig. 2 ▸(a). We will refer to these as the ‘closed conformation’ [Fig. 2 ▸(a), Class 1, EMDB entry EMD-11336] and the ‘open conformation’ [Fig. 2 ▸(a), Class 2, EMDB entry EMD-11337]. The number of images in each class was reduced to 45 000 in one case and 21 000 in the other, with global FSC-based resolutions of 3.1 and 3.3 Å, respectively.