(A) AcrB-SMALP from E. coli [14]. Representative 2D classes for the AcrB single-particle cryo-EM dataset side views of AcrB-SMALP and high angle views shown on the top and bottom row, respectively. The corresponding particle number in each class is shown on the bottom left. The white scale bar represents 100 Å. (B) The AcrB- SMALP 8.8 Å single-particle reconstruction coloured by local resolution and shown as a surface (left) and slice through (right). (C) Two representative 2D class average images of the ACIII in a supercomplex with an aa3-type cytochrome c oxidase (cyt aa3) from Flavobacterium johnsonia, in an SMALP nanodisc [28]. (D) Side (left) and top (right) views of the ACIII–cyt aa3 supercomplex cryo-EM map. The transparent surface indicates the boundary of the nanodisc. Scale bars, 50 Å.