Structural superimposition of LukE and LukD on the protomers of the HlgAB pore complex. (a) Superimposition of LukE (blue) and LukD (red) on the protomers HlgA and HlgB, respectively, in the pore complex (PDB entry 3b07, gray; Yamashita et al., 2011) reveals interface 1 and interface 2. (b) Interprotomer electrostatic interactions in the cap. Residues from HlgA and HlgB that form electrostatic interaction (gray sticks) are conserved in LukE (slate sticks) and LukD (red sticks). (c) Interprotomer electrostatic interactions in the rim. The conserved residues from HlgA and HlgB that form electrostatic interactions in the pore complex are superimposed in LukE and LukD. Sticks are colored as in (a).