Fig. 1
Architecture of apo and Mn-substituted M. tuberculosis PgsA1. a Transmembrane helices are numbered (1–6) and colored in rainbow, blue—N terminus, red—C terminus. b–e Metal binding sites in the PgsA1 dimer probed by Mn-substitution and anomalous scattering difference maps. Metal binding site 2 in chain B show dynamics with two possible metal binding positions suggesting metal ion mobility depending on ligand binding in the proximal hydrophilic pocket. Anomalous difference density around Mn ions is contoured at 4 σ and shown as a purple mesh. Fo−Fc omit electron density map for the bound citrates (in orange sticks) is contoured at 3.0 σ and shown as a gray mesh. Black lines denote metallic bonds. f Structural differences between apo (blue) and Mn-containing (green) structures are indicated with red arrows. Similar structural flexibility is observed in the second protomer of the dimer. Citrate and citrate-chelated metal ions are omitted for clarity. Manganese ions are shown as purple spheres, solvent molecules—as smaller red spheres
