Fig. 4.

3D density maps of TatAd complexes. (A) Shown from left to right are Classes 1–4. The maps are filtered to 30 Å and contoured at ~ 4σ (standard deviations above the mean density). Scale bar = 10 nm. (B) Cross-section of a Class 4 complex to show the internal cavity. In order to illustrate the compatible size and shape of TatAd monomers with this map, the solution state NMR structures of TatAd have been placed manually into the 3D density. Separate monomers are coloured in red, yellow, green and blue. Side views in (A) and (B) are shown with the potential cytoplasmic side facing down as suggested by the fitted TatAd NMR structure. TMH, transmembrane helix; APH, amphipathic helix.