Figure 2. Averaged subtomograms of Birbeck granules.

(A) Result of the initial 3D refinement. The central langerin trimer (blue) binds to the three inverted langerin trimers (red). (B) Result of the focused refinement. Improved resolution (6.4 Å) allowed secondary structure modeling. The gray mesh and the cyan surface indicate low and high threshold isosurfaces, respectively. (C) Result of the two-body refinement. The second body (orange) was refined with respect to the first body (cyan). (D) Honeycomb model of the langerin lattice within Birbeck granules. This honeycomb lattice is an ideal model, with the assumption of structural uniformity. (A–D) left, top views; right, side views.

Figure 2—figure supplement 1. Cryo-electron tomography of Birbeck granules.

(A) Summary of image processing. (B) Fourier shell correlation plot of the 3D refined structure of the langerin trimer, corresponding to the map in Figure 2C. The estimated resolution was 6.4 Å with a cut-off value of 0.143. The inset shows the local resolution map. (C) Angular distribution of the subtomograms. Although there was a strong bias toward the top-view direction, twisting of some granules (Figure 1—figure supplement 1C) provided side views.

Figure 2—video 1. Movie representation of the langerin lattice.

Download video file ^{(16.7MB, mp4)}