Molecular Playground/Transferrin: Difference between revisions
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<scene name='User:Khaja_Muneeruddin/Sandbox_1/Apotf/2'>Human Transferrin (hTf)</scene> is a 80 KDa bilobal, iron binding glycoprotein found in blood. In Apo hTf (iron free form), N-lobe (brown) and C-lobe (green) bind one ferric ion each to regulate the concentration of free iron in blood and also transport to iron requiring cells. | <scene name='User:Khaja_Muneeruddin/Sandbox_1/Apotf/2'>Human Transferrin (hTf)</scene> is a 80 KDa bilobal, iron binding glycoprotein found in blood. In Apo hTf (iron free form), N-lobe (brown) and C-lobe (green) bind one ferric ion each to regulate the concentration of free iron in blood and also transport to iron requiring cells. | ||
N-lobe and C-lobe are homologous and contain identical iron binding amino acid residues. Structurally both N-lobe and C-lobe contain two sub domains namely NI and NII, and CI and CII which come together to form a cleft for binding iron. At the <scene name='User:Khaja_Muneeruddin/Sandbox_1/Nlobe_binding_sites/3'>binding site of N-lobe</scene> Asp63, Tyr188, Tyr95, His249 and Arg124 are involved in trapping of iron<ref>PMID: 9609685</ref>. The amino acids involved in trapping of iron at the <scene name=' | N-lobe and C-lobe are homologous and contain identical iron binding amino acid residues. Structurally both N-lobe and C-lobe contain two sub domains namely NI and NII, and CI and CII which come together to form a cleft for binding iron. At the <scene name='User:Khaja_Muneeruddin/Sandbox_1/Nlobe_binding_sites/3'>binding site of N-lobe</scene> Asp63, Tyr188, Tyr95, His249 and Arg124 are involved in trapping of iron<ref>PMID: 9609685</ref>. The amino acids involved in trapping of iron at the <scene name='47/477021/N_lobe_fe_release/3'>binding site</scene> of C-lobe include Asp392, Tyr426, Tyr517, His585, Arg456<ref>PMID: 15924420</ref>. In addition to these amino acids, at both the lobes a carbonate ion also plays an important role in binding iron. At low pH iron is released from N-lobe by protonation of <scene name='Molecular_Playground/Transferrin/N_lobe_fe_release/2'>Lysines</scene> 206 and 296 <ref>PMID: 9609685</ref> and Lys534 and Arg632 in C-lobe.<ref>PMID: 19917294</ref> | ||
After binding iron N-lobe and C-lobe undergo a conformational change. In ApohTf, N lobe has an <scene name='User:Khaja_Muneeruddin/Sandbox_1/Opennlobe/2'>open conformation</scene> and upon binding ferric ion it shows a <scene name='User:Khaja_Muneeruddin/Sandbox_1/Closed/2'>closed conformation</scene> characterized by rotation of N-II sub domain by 63°<ref>PMID: 9760232</ref>. C-lobe also undergo a similar conformational change upon binding ferric ion, however crystal structure information of the C lobe of hTf is limited due to difficulty in production<ref>PMID: 9337853</ref>. | After binding iron N-lobe and C-lobe undergo a conformational change. In ApohTf, N lobe has an <scene name='User:Khaja_Muneeruddin/Sandbox_1/Opennlobe/2'>open conformation</scene> and upon binding ferric ion it shows a <scene name='User:Khaja_Muneeruddin/Sandbox_1/Closed/2'>closed conformation</scene> characterized by rotation of N-II sub domain by 63°<ref>PMID: 9760232</ref>. C-lobe also undergo a similar conformational change upon binding ferric ion, however crystal structure information of the C lobe of hTf is limited due to difficulty in production<ref>PMID: 9337853</ref>. | ||
Intracellular delivery of iron by transferrin is carried out by clathrin-dependent receptor-mediated endocytosis. At pH 7.4 diferric human transferrin binds to human transferrin receptor (hTfR). Upon binding, diferric hTf-hTfR is internalized and in the acidic condition of endosome iron is release from diferric hTf-hTfR complex into the cells. Apo hTf-hTfR complex is recycled back to the cell surface and at pH of cell surface Tf dissociates from the TfR to bind iron again.<ref>PMID: 16271884</ref><ref>PMID: 6300904</ref>. | |||
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[[Transferrin]] | [[Transferrin]] | ||
==References== | ==References== | ||
<references/> | <references/> | ||