a, The class 1 model of the SSRP1 MD (red ribbon) does not fit into the class 2 map (grey). The contour level of the map is 0.153. Left, the entire map. The orange oval highlights how the class 1 model overlaps with the density assigned to H2A–H2B. Right, close-up of the fit between the class 1 model and class 2 density for the SSRP1 MD. Arrows highlight problematic fits; a substantial part of the PH2 domain is outside of the density, and other parts of the density are empty. The correlation between model 1 (from class 1) and map 2 for the entire SSRP1 MD is 0.84 (calculated using UCSF Chimera). b, The class 2 model of the SSRP1 MD (purple ribbon) fits into the class 2 density map (grey). The contour level of the map is 0.153. Left, the entire map; no clashes are identified. Right, close-up of the fit between the model and density for the SSRP1 MD. Arrows indicate the same parts of the model or map as in a. The correlation between model 2 (from class 2) and map 2 for the entire SSRP1 MD is 0.93 (calculated using UCSF Chimera). c, Local-resolution heat map for the class 2 map. The resolution of the highlighted region (the PH2 domain from the SSRP1 MD at interface 2) is between 9 Å and 10 Å. The contour level is 0.177. d, Relative movement of the highlighted region (the PH2 domain of the SSRP1 MD at interface 2) between class 1 and 2 models. The distances or movements of the same amino acids in the two models (dotted ovals in c, d) are indicated.