(A) Sequence and secondary structure assignment of MCP. α-helices are marked by cylinders, β-strands by arrows, and loops by thin lines. The three structural elements of the Johnson fold, including N-, β- and α-elements, are shown in cyan, purple and green, respectively. (B) CryoEM density map of MCP (3.4 Å resolution, average of the six hexon MCP subunits in an asymmetric unit) shown as shaded surface using the same color coding of (A). The dashed box is shown in stereo in (D) contains the point of permutation (yellow arrow). See also Videos 3 and 4. (C) Ribbon diagram of the MCP atomic model with the three structural elements of the Johnson fold colored as in (A). (D) BPP-1 MCP density within the dash-box drawn in (B), showing the positions of the permutation (indicated by a yellow arrow in [B]) through which the N-element (cyan) is connected to the β-element (purple), instead of to helix α5 (green, far away), as in HK97 gp5. (E) CryoEM density (mesh) of the βG strand in (D) superimposed with its atomic model (sticks). (F) CryoEM density (mesh) of the α5 helix in (D) superimposed with its atomic model (ribbon with sticks).