Fig. 4. Stereo view illustrating the location, within the active site, of the sulfate ion (SUL) and the imidazole molecule (IMD). The Mn²⁺ ion (in purple) and its coordination site composed of H25, H32, H69 and E114 and E116 are shown, as well as S36, Y104 and W161 at the bottom of the active site. K21, K55 and R51 interact with the sulfate ion. Buried water molecules are located between an ionic cluster composed of K55, E87, R83, E4 and K21 and the catalytic C67. The water molecule hydrogen bonded to E87 is indicated (WAT).