(A) SDS-PAGE from sucrose gradient purification of P4 procapsids. The lanes are labeled by fraction number, and the arrow shows the direction of sedimentation. Positions of bands corresponding to gpN, gpO and Sid are indicated. M = marker, with pertinent molecular weights (kDa) listed. (B) Cryo-electron micrograph of P4 procapsids. The arrows point to additional proteinaceous material assumed to be Sid. Scale bar, 100 nm. (C) Fourier Shell Correlation (FSC) plots for the icosahedral (blue) and asymmetric (red) reconstructions calculated in RELION, for the asymmetric map calculated in Phenix (green) and the correspondence between the atomic model and the reconstruction (yellow), calculated in Phenix. The gray lines show the 0.143 and 0.5 cutoff levels.