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Figure 2
Single-particle helical reconstruction from (−17, 5) tubes. (a) Masked-out volume showing the helical arrangement of ACh receptors; a δ–δ linked dimer of receptors and a ribbon of dimers are shaded in pink and grey, respectively. (b) Central cross-section (top) and radial section (bottom) from the three-dimensional density map cutting through receptors and the lipid-bilayer matrix in which they are embedded. (c) Enlargements of regions in (b) with atomic models of the ACh receptor (PDB entry 2bg9) superimposed. Circles identify areas next to the δ subunit where densities corresponding to the outer phospholipid headgroups are weak or missing; the adjacent helices are M1 (lower circle), and M4 and M1 (upper circle). Subunit colours: αγ, red; αδ, orange; β, green; γ, cyan; δ, blue. Inverted contrast.

IUCrJ
Volume 4| Part 4| July 2017| Pages 393-399
ISSN: 2052-2525
https://doi.org/10.1107/S2052252517005243