[1H,13C] NMR determination of the order of lobe loading of human transferrin with iron: comparison with other metal ions.
Human serum transferrin (hTF) is a single-chain bilobal glycoprotein (80 kDa) which transports Fe3+ and a variety of other metal ions in blood. Only diferric transferrin, not the apo-protein, binds strongly to transferrin receptors and is taken up by cells via receptor-mediated endocytosis. We show here that 2D [1H,13C] NMR studies of recombinant epsilon-[13C]Met-hTF allow the order of lobe loading with various metal ions, including Fe3+, to be determined. In particular, the resonance for Met-464, a residue in the hydrophobic patch of helix 5, is very sensitive to iron binding in the C-lobe. The selectivity of lobe loading with Fe3+ is compared to loading with Fe2+ (which binds as Fe3+), Al3+, Ga3+ and Bi3+. Similar changes in shifts of the Met residues are observed for these metal ions, suggesting that they induce similar conformational changes in the protein.
Sun
H
H
Department of Chemistry, University of Edinburgh, UK.
Cox
M C
MC
Li
H
H
Mason
A B
AB
Woodworth
R C
RC
Sadler
P J
PJ
D000535:Aluminum / Q000737:chemistry; D000818:Animals; D001729:Bismuth / Q000737:chemistry; D002478:Cells, Cultured; D006224:Cricetinae; D005290:Ferric Compounds / Q000737:chemistry; D005708:Gallium / Q000737:chemistry; D006801:Humans; D007501:Iron / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008670:Metals / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D014168:Transferrin / Q000737:chemistry* / Q000235:genetics
D005290:Ferric Compounds; D008670:Metals; D011994:Recombinant Proteins; D014168:Transferrin; D005708:Gallium; D000535:Aluminum; D007501:Iron; D001729:Bismuth