A naturally occurring omega current in a Kv3 family potassium channel from a platyhelminth |
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Authors: | Tara L Klassen Andrew N Spencer Warren J Gallin |
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Institution: | (1) Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6J 2E9, Canada;(2) Malaspina University College, 900 Fifth Street, Nanaimo, British Columbia, V9R 5S5, Canada |
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Abstract: | Background Voltage-gated ion channels are membrane proteins containing a selective pore that allows permeable ions to transit the membrane
in response to a change in the transmembrane voltage. The typical selectivity filter in potassium channels is formed by a
tetrameric arrangement of the carbonyl groups of the conserved amino-acid sequence Gly-Tyr-Gly. This canonical pore is opened
or closed by conformational changes that originate in the voltage sensor (S4), a transmembrane helix with a series of positively
charged amino acids. This sensor moves through a gating pore formed by elements of the S1, S2 and S3 helices, across the plane
of the membrane, without allowing ions to pass through the membrane at that site. Recently, synthetic mutagenesis studies
in the Drosophila melanogaster Shaker channel and analysis of human disease-causing mutations in sodium channels have identified amino acid residues that
are integral parts of the gating-pore; when these residues are mutated the proteins allow a non-specific cation current, known
as the omega current, to pass through the gating-pore with relatively low selectivity. |
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