Anion binding properties of the transferrins. Implications for function

► A wide variety of anions bind to apoTf. ► A few of these anions are synergistic and support the binding of iron(III). ► Conformational changes in the synergistic anion are critical for iron release. ► Competition from non-synergistic anions in vivo affects transferrin function. ► There are multiple allosteric anion binding sites that affect iron release.