Molecular aspects of the binding of absorbed iron to transferrin

To study the molecular aspects of the binding of absorbed iron to plasma transferrin, 59Fe with high specific activity was administered via intragastric tube to iron-deficient rabbits. The distribution of the absorbed 59Fe among the molecular forms of iron-transferrin was analysed using urea-polyacrylamide gel electrophoresis. Absorbed iron was bound to circulating transferrin one atom at a time. In four out of five animals, absorbed iron was predominantly bound to the site in the N-terminal domain of the protein. Thus, the two sites of transferrin may differ in their ability to load absorbed iron.