FIGURE 6.

ROP5 uses a polymorphic surface to bind IRGa6. A, overview of the ROP5-IRGa6 structure. ROP5 is shown as a black surface with polymorphic residues shaded green or yellow (the latter are in the pseudoactive site). IRGa6 is shown in orange. B, an alignment of regions of ROP5 sequence that are hotspots of polymorphism (green shading) and involved in the interaction with IRGa6. C, a phylogenetic tree of five ROP5 alleles in which all residues not located at the interface with IRGa6 were held constant. D, pairwise comparison of different ROP5 alleles reveals that all alleles of ROP5 appear to have experienced diversifying selective pressure on the interface with IRGa6 (polymorphic interface residues shaded green; note that the orientation of ROP5 shown in A has been rotated to show the full binding surface in D). The numbers of polymorphic residues at the IRGa6 interface versus in the entire sequence are indicated.