Anion, cation, and zwitterion selectivity of phospholemman channel molecules. |
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Authors: | G C Kowdley S J Ackerman Z Chen G Szabo L R Jones J R Moorman |
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Affiliation: | Department of Internal Medicine (Cardiovascular Division), University of Virginia Health Sciences Center, Charlottesville 22908, USA. |
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Abstract: | Phospholemman (PLM), a 72-amino acid membrane protein with a single transmembrane domain, forms taurine-selective ion channels in lipid bilayers. Because taurine forms zwitterions, a taurine-selective channel might have binding sites for both anions and cations. Here we show that PLM channels indeed allow fluxes of both cations and anions, making instantaneous and voltage-dependent transitions among conformations with drastically different ion selectivity characteristics. This surprising and novel ion channel behavior offers a molecular explanation for selective taurine flux across cell membranes and may explain why molecules in the phospholemman family can induce cation- or anion-selective conductances when expressed in Xenopus oocytes. |
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