Calcium-induced potassium pathway in sided erythrocyte membrane vesicles |
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Authors: | Heven Sze AK Solomon |
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Institution: | Biophysical Laboratory, Harvard Medical School, 25 Shattuck Street, Boston, MA 02115 U.S.A. |
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Abstract: | We have characterized the asymmetric effect of Ca2+ on passive K+ permeability in erythrocyte membranes, using inside out and right-side out vesicles. Ca2+, but not Mg2+, can induce an increase in K+ uptake in inside out vesicles. The half-maximal concentration of Ca2+ required to induce the K+ uptake is 0.2 mM, and the permeability increase is not specific for K+. Thus, the Ca2+-induced permeation process in inside out vesicles is changed from that in the energy-depleted intact cell which requires only micromolar concentrations of Ca2+ and is specific for K+. Removal of spectrin had no effect on the vesicle permeability increase due to Ca2+. Studies with show that the vesicle channel opening is mediated by a protein and passage is controlled by sulfhydryl groups; furthermore, the Ca2+-induced vesicle pathway is distinct from the normal channel for passive K+ leak in the absence of Ca2+. The protein is sensitive to its phospholipid environment since removal of easily accessible phospholipid head groups on the cytoplasmic face of the vesicles inhibits the Ca2+-stimulated channel opening. |
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Keywords: | Permeability Sidedness (Erythrocyte membrane vesicle) |
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