Structure of the human transferrin receptor-transferrin complex.
Iron, insoluble as free Fe(3+) and toxic as free Fe(2+), is distributed through the body as Fe(3+) bound to transferrin (Tf) for delivery to cells by endocytosis of its complex with transferrin receptor (TfR). Although much is understood of the transferrin endocytotic cycle, little has been uncovered of the molecular details underlying the formation of the receptor-transferrin complex. Using cryo-electron microscopy, we have produced a density map of the TfR-Tf complex at subnanometer resolution. An atomic model, obtained by fitting crystal structures of diferric Tf and the receptor ectodomain into the map, shows that the Tf N-lobe is sandwiched between the membrane and the TfR ectodomain and that the C-lobe abuts the receptor helical domain. When Tf binds receptor, its N-lobe moves by about 9 A with respect to its C-lobe. The structure of TfR-Tf complex helps account for known differences in the iron-release properties of free and receptor bound Tf.
Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
Yifan
Y
Cheng
Olga
O
Zak
Philip
P
Aisen
Stephen C
SC
Harrison
Thomas
T
Walz
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D020285:Cryoelectron Microscopy; D004583:Electrons; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007501:Iron / Q000737:chemistry / Q000378:metabolism; D008854:Microscopy, Electron; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011990:Receptors, Transferrin / Q000737:chemistry*; D013997:Time Factors; D014168:Transferrin / Q000737:chemistry*
D011990:Receptors, Transferrin; D014168:Transferrin; D007501:Iron