Autoradiographic Localization of ¹²⁵I-Labelled Transferrin in Rabbit Reticulocytes

Abstract

THE first step in the transfer of iron from the plasma iron-carrying protein, transferrin, to reticulocytes and probably to other erythropoietic cells, is the binding of transferrin to the cells^1,2. After release, the iron from transferrin enters the haem synthesis pathway, while the transferrin is released from the cell. The transferrin binding occurs in two stages, an initial rapid, temperature insensitive stage, probably adsorption to the cell membrane, and a slower temperature dependent stage which results in a firmer union of the transferrin to the cell³. Little is known about the nature or the site of transferrin binding to reticulocytes. We report here that transferrin actually penetrates into the interior of the cell.