Redox properties of human transferrin bound to its receptor.
Biochemistry
; 43(1): 205-9, 2004 Jan 13.
Article
em En
| MEDLINE
| ID: mdl-14705946
ABSTRACT
Virtually all organisms require iron, and iron-dependent cells of vertebrates (and some more ancient species) depend on the Fe(3+)-binding protein of the circulation, transferrin, to meet their needs. In its iron-donating cycle, transferrin is first captured by the transferrin receptor on the cell membrane, and then internalized to a proton-pumping endosome where iron is released. Iron exits the endosome to enter the cytoplasm via the ferrous iron transporter DMT1, a molecule that accepts only Fe(2+), but the reduction potential of ferric iron in free transferrin at endosomal pH (approximately 5.6) is below -500 mV, too low for reduction by physiological agents such as the reduced pyridine nucleotides with reduction potentials of -284 mV. We now show that in its complex with the transferrin receptor, which persists throughout the transferrin-to-cell cycle of iron uptake, the potential is raised by more than 200 mV. Reductive release of iron from transferrin, which binds Fe(2+) very weakly, is therefore physiologically feasible, a further indication that the transferrin receptor is more than a passive conveyor of transferrin and its iron.
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Base de dados:
MEDLINE
Assunto principal:
Receptores da Transferrina
/
Transferrina
Limite:
Humans
Idioma:
En
Ano de publicação:
2004
Tipo de documento:
Article