The IncE sequence forms a long β-hairpin structure that binds within a complementary groove at the base of the extended α-helical insertion of the SNX5 PX domain and adjacent to the β-sheet sub-domain (Figure 4A; Video 2). The β-hairpin structure of IncE (N-terminal βA and C-terminal βB strands) is directly incorporated as a β-sheet augmentation of the β1, β2 and β3 strands of SNX5 (Figure 4B). The N-terminal βA strand of the IncE sequence (Gly111-Lys118) forms the primary interface with SNX5, making main-chain hydrogen bonds with the β1 strand of the SNX5 PX domain for the stable positioning of the IncE structure. The two anti-parallel β-strands of IncE are connected by a short loop (Gly119-Ala124) that makes no direct contact with the SNX5 protein, and the C-terminal IncE βB strand (Asp125-Val130) forms an interface with the extended α-helical region of the SNX5 PX domain.Video 2.Animation highlighting the mechanism of interaction between SNX5 and IncE.The SNX5 PX domain is shown in yellow ribbons and the IncE peptide is shown in magenta.DOI: http://dx.doi.org/10.7554/eLife.22311.01410.7554/eLife.22311.014