Structural and functional studies on the stalk of the transferrin receptor |
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Authors: | Danijela Dukovski Zongli Li Deborah F Kelly Thomas Walz |
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Institution: | a Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA b Howard Hughes Medical Institute, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA c Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA |
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Abstract: | Transferrin (Tf) is an iron carrier protein that consists of two lobes, the N- and C-lobes, which 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 suggested that the TfR stalks could form additional contacts with the Tf N-lobes, thus potentially further slowing down its iron release. Here, we show that the TfR stalks are unlikely to make strong interactions with the Tf N-lobes and that the stalks have no effect on iron release from the N-lobes of receptor-bound Tf. |
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Keywords: | Transferrin Transferrin receptor Receptor stalk Iron release Single particle electron microscopy |
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