Protomer tilts in the OFS. Trimers were superimposed on the trimerization regions (residues 150–195) of all three protomers. (a–c) Comparison of the tilts for OFS_out/OFS_mid (a); OFS_mid/OFS_in (b); and OFS_out/OFS_in (c). OFS_out, OFS_mid, and OFS_in are purple, green, and blue, respectively. Although parts of the scaffold domain also move (see Videos 2, 3, and 4), only transport domains of the classified protomers are shown for clarity. Black bars represent tilt axes and angles calculated using the align command in ChimeraX. The corresponding per-residue Cα RMSDs are on the right. Transmembrane domains are labeled and alternatively shaded. L, the flexible loop between TM3 and TM4.