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Binding of apotransferrin to K562 cells: explanation of the transferrin cycle. 1983

R D Klausner, and G Ashwell, and J van Renswoude, and J B Harford, and K R Bridges

The binding of apotransferrin to the transferrin receptor on the surface of human leukemic K562 cells was found to be significantly less tight than that of the holoprotein, diferric transferrin. The finding that both ligands displayed linear Scatchard plots with similar receptor number (approximately equal to 150,000 per cell) and mutually inhibit each other's binding suggested that they bind to the same receptor. Both the dissociation and association rate of apotransferrin were markedly increased (28-fold and 15-fold, respectively) at pH 7.2 compared to pH 4.8. Using the values of these binding parameters, we propose a mechanism to account for the recycling of transferrin subsequent to internalization and residence within an acidic nonlysosomal organelle where iron is removed.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D011956 Receptors, Cell Surface Cell surface proteins that bind signalling molecules external to the cell with high affinity and convert this extracellular event into one or more intracellular signals that alter the behavior of the target cell (From Alberts, Molecular Biology of the Cell, 2nd ed, pp693-5). Cell surface receptors, unlike enzymes, do not chemically alter their ligands. Cell Surface Receptor,Cell Surface Receptors,Hormone Receptors, Cell Surface,Receptors, Endogenous Substances,Cell Surface Hormone Receptors,Endogenous Substances Receptors,Receptor, Cell Surface,Surface Receptor, Cell
D011990 Receptors, Transferrin Membrane glycoproteins found in high concentrations on iron-utilizing cells. They specifically bind iron-bearing transferrin, are endocytosed with its ligand and then returned to the cell surface where transferrin without its iron is released. Transferrin Receptors,Transferrin Receptor,Receptor, Transferrin
D002478 Cells, Cultured Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others. Cultured Cells,Cell, Cultured,Cultured Cell
D004705 Endocytosis Cellular uptake of extracellular materials within membrane-limited vacuoles or microvesicles. ENDOSOMES play a central role in endocytosis. Endocytoses
D004915 Leukemia, Erythroblastic, Acute A myeloproliferative disorder characterized by neoplastic proliferation of erythroblastic and myeloblastic elements with atypical erythroblasts and myeloblasts in the peripheral blood. Di Guglielmo's Disease,Erythremic Myelosis,Erythroblastic Leukemia, Acute,Erythroleukemia,Leukemia, Myeloid, Acute, M6,Myeloid Leukemia, Acute, M6,Di Guglielmo Disease,Acute Erythroblastic Leukemia,Acute Erythroblastic Leukemias,Di Guglielmos Disease,Disease, Di Guglielmo,Disease, Di Guglielmo's,Erythremic Myeloses,Erythroblastic Leukemias, Acute,Erythroleukemias,Leukemia, Acute Erythroblastic,Leukemias, Acute Erythroblastic,Myeloses, Erythremic,Myelosis, Erythremic
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D006863 Hydrogen-Ion Concentration The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D001059 Apoproteins The protein components of a number of complexes, such as enzymes (APOENZYMES), ferritin (APOFERRITINS), or lipoproteins (APOLIPOPROTEINS). Apoprotein
D014168 Transferrin An iron-binding beta1-globulin that is synthesized in the LIVER and secreted into the blood. It plays a central role in the transport of IRON throughout the circulation. A variety of transferrin isoforms exist in humans, including some that are considered markers for specific disease states. Siderophilin,Isotransferrin,Monoferric Transferrins,Serotransferrin,Transferrin B,Transferrin C,beta 2-Transferrin,beta-1 Metal-Binding Globulin,tau-Transferrin,Globulin, beta-1 Metal-Binding,Metal-Binding Globulin, beta-1,Transferrins, Monoferric,beta 1 Metal Binding Globulin,beta 2 Transferrin,tau Transferrin

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