Organization of HBs in the membrane. (A–D) Transmembrane region of compact particles (EMD-1399, EMD-1403, EMD-1404, EMD 1405); (E–G) transmembrane region of gapped particles (EMD-1406, EMD-1407, EMD-1408). Densities in the asymmetric unit are color-coded: blue, closest to the five-fold axes, red, closest to the two-fold axes and green close to the three-fold axes but weaker in some reconstructions. The common building principle is shown in (H). (I) Superposition of maps (A–D) (compact particles); (J) superposition of maps (E–G) (gapped particles). The superposition shows that without separating the particles according to their HBs-packing, an almost featureless envelope region is observed. (K, L) Envelope region of panel B, which had the lowest phase residuals in cross common lines of the compact maps after refinement. (K) Envelope seen from the outside and (L) envelope seen from the inside (see Supplementary Figure 6 for other envelopes of the other particle reconstructions).