Interaction of human diferric transferrin with reticulocytes.

Abstract
Methods were devised for preparing human transferrin with a different isotope of Fe, selectively labeling each of the 2 Fe binding sites, and for determining the distribution of radioiron among transferrin molecules. When diferric human transferrin was exposed to human or animal [rabbit or rat] reticulocytes, there was an equal contribution of radioiron from the acid-stable and acid-labile sites. In this delivery, both atoms of Fe were removed simultaneously from the diferric transferrin molecule, converting it to apotransferrin. At similar Fe concentrations the amount of Fe delivered by diferric transferrin was twice that delivered by monoferric transferrin.