C Analysis of the ferrous iron binding activity of DJA6. Isothermal titration calorimetry measurements of ferrous iron binding to apo DJA6 were carried out on a MicroCal iTC200. Fe2+ was titrated into a solution of 50 μM DJA6 or DJA6 variants. For the background titrations, the ferrous iron was titrated into the corresponding buffer. 