(A) Secondary structure model of the OMCC. The left panel represents view looking in from the outer membrane and the right panel represents the view looking out from the inner membrane. (A–C) Blue, CagY; Green, CagX; Red, CagT; Gold, I-layer; and Purple, O-layer. (B) Central axial slice view of the secondary structural model of the OMCC highlighting the position of CagY, CagX, CagT, I-layer, and O-layer. (C) Cryo-EM densities with built models of CagX, CagY, and CagT. Cryo-EM density map is in gray mesh and model is shown as ribbon diagram. (D) 3.5 Å resolution cryo-EM density map of the Cag T4SS PRC rotated 90° around the X-axis. The structure has 17-fold symmetry. (E) Secondary structure model of the PRC. Chain 1 (67 residues, green), Chain 2 (96 residues, blue) and Chain 3 (136 residues, red). In both D and E the left panel represents view looking in from outer membrane and right panel represents the view looking out from the inner membrane.