can each bind a Fe3+ ion. Tf binds to its receptor (TfR), which mediates iron delivery to cells
through an endocytotic pathway. Receptor binding facilitates iron release from the Tf C-lobe,
but impedes iron release from the N-lobe. An atomic model of the Tf–TfR complex based on
single particle electron microscopy (EM) indicated that receptor binding is indeed likely to
hinder opening of the N-lobe, thus interfering with its iron release. The atomic model also …