TBPP_transferrin
TBPP_transferrin
TBPP_transferrin
Kartei Details
Karten | 15 |
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Sprache | English |
Kategorie | Chemie |
Stufe | Universität |
Erstellt / Aktualisiert | 30.12.2016 / 05.01.2017 |
Lizenzierung | Keine Angabe |
Weblink |
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Haptoglobin (Hp) binds to free Hemoglobin, Hemopexin (Hx) binds to heme, Transferrin binds to iron, binding protects against damage. = transporter
glycoprotein, 79 kD, 679 AS, produced in liver, plasma concentration 2-4 g/L, 2 binding sites for ferric iron (Fe3+), iron saturation about 35%
Alpha-helices and Beta-sheets, 2 lobes: N- and C-lobe, each of them 2 subdomains: C1&C2, N1&N2, each lobe has one binding site for Fe3+, stabilized by 19 disulfide bonds, subdomains of lobs are discontinous, N- and C-lobe different AS: Tyr (2x), Asp, His, Arg to anchor carbonate.
empty transferrin: apotransferrin, 1 Fe3+: monoferric transferrin, 2 Fe3+: diferric transferrin, very high affinity for binding at pH 7,4 (in cytoplasm, outside the cell), binding is reversible at lower pH (inside of the cell)
expressed as a homo-dimer, 3 domains, "butterfly", binds iron-loaded transferrin with high affinity, each member of dimer can bind a molecule transferrin
to trasport iron between sites of adsorption, recycling, storage and utilization. Adsorption: small intestine (via food), recycling: spleen (degradation of erythrocytes), storage: liver, utilization: synthesis of heme in bone marrow
non-heme iron (Fe3+) must be reduced to get inside of the cell through Ferrireductase (at apical side) --> DMT1 mediates protondependent Fe2+ import --> HCP1 transports dietary heme iron --> heme oxygenase releases iron from protoporphyrin: entrance of the same pool as non-heme iron --> some iron stored within ferritin --> ferroportin exports some iron, where it is oxidized to Fe3+ for incorporation into transferrin (at basal side)
Fe3+: ferric, chemically inert, Fe2+: ferrous, highly reactive, fenton, only Fe2+ can be taken up by enterocyte receptors = need for ferric reductases, Fe3+ to enable binding by Transferrin