(A) 3NTDO-FDS2, the Rieske center and coordinating side chain residues are shown in stick representation. (B) 2Fo-Fc electron density contoured at 1.0 σ level in the Rieske cluster of ferredoxin shown as a ball and stick model and in blue wire mesh. (C) 3NTDO-ODS2, the three αsubunits are colored green, blue and red and β subunits are in yellow, grey and cyan. The Rieske center and the catalytic iron are shown in CPK model representation. (D) 2Fo-Fc electron density contoured at 1.5σ level in the vicinity of catalytic iron center with the ligand His206, His211 and Asp360 shown as a ball and stick model. (E) View along the molecular threefold axis of 3NTDO-ODS2. The iron, sulphur, nitrogen and water are shown in magenta, yellow, blue and red colors, respectively.