Transmembrane Ca2+ gradient is essential for high anion transport activity of human erythrocytes.
The role of a transmembrane Ca2+ gradient in anion transport by Band 3 of human resealed erythrocyte ghosts has been studied. The results show that a transmembrane Ca2+ gradient is essential for the conformation of erythrocyte Band 3 with higher anion transport activity. The dissipation of the transmembrane Ca2+ gradient by the ionophore A23187 inhibits the anion transport activity. The extent of this inhibition approaches 90% as the Ca2+ concentration on both sides of the ghost membrane is increased to 1.0 mM and half-maximum inhibitions is observed at 0.25 mM Ca2+. Addition of ATP (0.4 mM) to the resealing medium can partly reestablish the transmembrane Ca2+ gradient by activation of Ca(2+)-ATPase and alleviate the inhibition to some extent. N-ethylmaleimide, an inhibitor of erythrocyte Ca(2+)-ATPase, prevents such restoration. Electron micrographs reveal that numerous larger intramembranous particle can be observed on the P-faces of freeze-fractured resealed ghosts in the absence of a transmembrane Ca2+ gradient.
Center of Experimental Technology, Academia Sinica, Beijing, China.
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D001457:Anion Exchange Protein 1, Erythrocyte / Q000737:chemistry / Q000378:metabolism*; D000838:Anions / Q000378:metabolism; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D004910:Erythrocyte Membrane / Q000378:metabolism*; D006801:Humans; D011487:Protein Conformation
D001457:Anion Exchange Protein 1, Erythrocyte; D000838:Anions; D002118:Calcium