FIGURE 7.

Proposed steps in the substrate binding process of the DK17 AkbC enzyme. A, without substrate, the iron coordinates with four residues and a water molecule. B, 3-MC binds first to one oxygen atom in the empty axial position in the opposite site of Glu-263. C, by correcting the position of 3-MC with both oxygen atoms as equatorial ligands, the water molecule and Tyr-253 are retracted from the iron, leaving the axial binding position empty. D, an oxygen molecule binds the empty position.