Two Distinct Mechanisms of Transport Through the Plasmodial Surface Anion Channel

Two Distinct Mechanisms of Transport Through the Plasmodial Surface Anion Channel The plasmodial surface anion channel (PSAC) is a voltage-dependent ion channel on erythrocytes infected with malaria parasites. To fulfill its presumed function in parasite nutrient acquisition, PSAC is permeant to a broad range of charged and uncharged solutes; it nevertheless excludes Na+ as required to maintain erythrocyte osmotic stability in plasma. Another surprising property of PSAC is its small single-channel conductance (<3 pS in isotonic Cl−) in spite of broad permeability to bulky solutes. While exploring the mechanisms underlying these properties, we recently identified interactions between permeating solutes and PSAC inhibitors that suggest the channel has more than one route for passage of solutes. Here, we explored this possibility with 22 structurally diverse solutes and found that each could be classified into one of two categories based on effects on inhibitor affinity, the temperature dependence of these effects and a clear pattern of behavior in permeant solute mixtures. The clear separation of these solutes into two discrete categories suggests two distinct mechanisms of transport through this channel. In contrast to most other broad-permeability channels, selectivity in PSAC appears to be complex and cannot be adequately explained by simple models that invoke sieving through rigid, noninteracting pores. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Two Distinct Mechanisms of Transport Through the Plasmodial Surface Anion Channel

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Publisher
Springer-Verlag
Copyright
Copyright © 2008 by National Institutes of Health
Subject
Life Sciences; Human Physiology ; Biochemistry, general
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-008-9136-2
Publisher site
See Article on Publisher Site

Abstract

The plasmodial surface anion channel (PSAC) is a voltage-dependent ion channel on erythrocytes infected with malaria parasites. To fulfill its presumed function in parasite nutrient acquisition, PSAC is permeant to a broad range of charged and uncharged solutes; it nevertheless excludes Na+ as required to maintain erythrocyte osmotic stability in plasma. Another surprising property of PSAC is its small single-channel conductance (<3 pS in isotonic Cl−) in spite of broad permeability to bulky solutes. While exploring the mechanisms underlying these properties, we recently identified interactions between permeating solutes and PSAC inhibitors that suggest the channel has more than one route for passage of solutes. Here, we explored this possibility with 22 structurally diverse solutes and found that each could be classified into one of two categories based on effects on inhibitor affinity, the temperature dependence of these effects and a clear pattern of behavior in permeant solute mixtures. The clear separation of these solutes into two discrete categories suggests two distinct mechanisms of transport through this channel. In contrast to most other broad-permeability channels, selectivity in PSAC appears to be complex and cannot be adequately explained by simple models that invoke sieving through rigid, noninteracting pores.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Dec 3, 2008

References

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