Fig. 2. Molecular details of IMC protein structures and interactions.

a, Overall structure of the IMC. The IMC is shown in ribbon representation, with subunits coloured dark blue (VirB4_central), cyan (VirB4_outside), pale green (VirB3) and yellow (VirB8_tails). Left, side view of the IMC. The external dimensions of the central VirB4 hexamer and of the IMC are indicated, as well as the position of the inner membrane derived from the density. Right, top view of the IMC. The IMC protomer and the central hexamer are shown in a dashed red oval and dark blue circle, respectively. A schematic diagram of the hexamer of VirB4 dimers is shown on the right. b, Overall structure of the IMC protomer. Proteins are shown and colour-coded as in a. The boxes locate the regions detailed in c–e. c, Details of the interactions between subunits within the VirB4 dimer. VirB4_central is shown in ribbon and semi-transparent surface in dark blue and VirB4_outside is shown in cyan ribbon. All secondary structures involved in the interactions are shown. d, Details of the interactions between VirB4 and VirB3. VirB4_central is shown in dark blue ribbon and surface representation and VirB3 is shown in pale green ribbon. All secondary structures containing residues involved in the interaction are labelled. e, Details of the interactions between VirB4_outside and two of the VirB8_tails. Only two are shown because although three VirB8_tails form a three-helix bundle, one of the helices makes very few interactions with VirB4_outside. The two VirB8_tails (VirB8_tailsA and VirB8_tailsB) are shown in yellow and wheat ribbons, respectively. VirB4_outside is shown in cyan ribbon and its semi-transparent surface is coloured yellow or wheat according to the VirB8_tail that it interacts with, or cyan for non-interacting surfaces.