Figure 1. Crystal structures of PIBO and IPPA.

(A) Schematic diagram of the structure of PIBO (PDB code 3n8u) color-coded from N-terminus (blue) to C-terminus (red) in two orientations. Helices are represented as tubes and labeled A to R (3₁₀ helices are not labeled). His368 and Glu371 of the GxHxxE motif are shown as sticks. (B) Schematic diagram of the structure of IPPA (PDB code 3pf0) color-coded from N-terminus (blue) to C-terminus (red) in the same orientation as PIBO. Helices are represented as tubes and labeled A to M (3₁₀ helices are not labeled). Pro194 and Glu197 of the GxxxxE motif are shown as sticks.