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. 2018 Aug 10;7:e38461. doi: 10.7554/eLife.38461

Figure 2. Subunit arrangement exhibits symmetry mismatch.

(A) SWELL1 model viewed from the membrane plane with domain layers viewed perpendicular to the symmetry axis. (B–C) Domain layers viewed from the top of the channel grouped according to shared symmetry with simple schematic to demonstrate subunit arrangement. (B) From left to right: extracellular domain layer (EC), transmembrane domain layer (TM), and intracellular linker domain layer (ICL) all share the same 6-fold rotation symmetry axis (black hexagon). (C) The LRR domain layer has 3-fold rotational symmetry (black triangle), resulting from parallel pairing of three sets of LRR domains. (D) Asymmetry in LRR pairing arises from a hinge at L402 on LH8 that allows rotation of the LRR domain as a rigid body in a dimer pair. The first two TM domains of the inner (red) and outer (yellow) subunits are aligned to one another using the PyMOL align function.

Figure 2.

Figure 2—figure supplement 1. Flexibility in LRR domains observed during 3D classification.

Figure 2—figure supplement 1.

Bottom view of arrangement of LRR domains in representative subclasses of density-subtracted 3D classification (see Materials and methods). Pre-cleaned particle picks were distributed into classes with clear organization of three (A; 25,607 particles), two and one half (B; 29,638 particles), two (C; 7197 particles), and one (D; 8071 particles) pairs of LRRs are observed. The highest resolution map was produced with the particles in the classes in which all three pairs are resolved, while the classes in which one or more LRR pairs are flexible produce lower resolution refinements. (E) Example refinement of LRR class (B) with two and one half LRR pairs resolved and one LRR flexible (~5.7 Å resolution).