(a) Ligand used for cocrystallization with S25-2: Kdo-(2→4)-5,6-dehydro-Kdo. (b) Structure of chlamydial LPS composed of Kdo-(2→8)-Kdo-(2→4)-Kdo-(2→6)-GlcN4P-(1→6)-GlcN1P. The Kdo-(2→4)-Kdo that previously cocrystallized with S25-2 (PDB entry 3t77
; Nguyen et al., 2003) is highlighted in red. (c) 2Fo − Fc electron-density map contoured to 1σ around Kdo-(2→4)-5,6-dehydro-Kdo cocrystallized with S25-2.