Furthermore, it's unclear whether both histidine ligands would still be bound to ferric iron, as they would be needed for proper iron positioning in the active site for native activity. Saturation of coordination sites by DOPA121 would also prevent cofactors like 2OG and oxygen from binding to the iron site. Occupancy of coordination sites by pyruvate, as shown in our MS studies, would also exacerbate this problem. Overall, the sequestration of ferric iron by the modified DOPA residue abolishes any catalytic activity of SyrB2.