Iron removal from transferrin. An experimental study.

We have studied the facilitation of iron transfer from transferrin to desferrioxamine by various anions. Most of the anions which can substitute for HCO-3 in the ternary complex of transferrin - Fe - HCO3 do not facilitate iron transfer; anions which do facilitate iron transfer do not necessarily form stable ternary complexes. Combinations of anions effective in transfer have a less-than-additive effect, suggesting a common reaction pathway. We suggest that the transfer of iron from transferrin to desferrioxamine involves a substitution step and a subsequent chelation step, and that the efficiency of the overall reaction is a function of both these attributes of the anion.