Mapping of extra density on the surface of PP7-a-loop-PP7, PP7-PP7-ZZ, and PP7-a-loop-PP7–150-loop particles. Overall surface density maps: (A) PP7-PP7-ZZ, (B) PP7-a-loop-PP7, and (C) PP7-a-loop-PP7–150-loop. Extra densities highlighted: (D) PP7-PP7-ZZ, (E) PP7-a-loop-PP7, and (F) PP7-a-loop-PP7–150-loop, comparing to PP7-PP7. (G) PP7-PP7-ZZ, (H) PP7-a-loop-PP7, and (I) PP7-a-loop-PP7–150-loop, showing the same loop insertions and C-terminal extensions as in (D–F). Subunit organization in (G–I) is indicated as in Figure 5.