Nature 1994 Jan 13;3676459:179-82. doi: 10.1038/367179a0.

Evidence that the S6 segment of the Shaker voltage-gated K+ channel comprises part of the pore.

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Potassium channels are highly selective and allow the rapid flux of potassium ions through their pore. Several studies have implicated the H5 (P or SS1-SS2) segment as part of the pore in voltage-gated ion channels. The proposal that H5 spans at least 80% of the electric potential drop across the K+ channel pore is based on altered internal tetraethylammonium sensitivity arising from mutations of H5 residues that are 100% conserved among K+ channels having differing sensitivity to tetraethylammonium. Here we report that the S6 segment is also involved in K+ ion permeation and in governing the sensitivity to internal tetraethylammonium and barium. Transplanting the S6 segment of NGK2 into Shaker causes this S6 chimaera to adopt the single-channel conductance and sensitivity to internal tetraethylammonium and barium ions from the NGK2 channel. The differences between NGK2 and Shaker in external tetraethylammonium sensitivity, but not single-channel conductance, can be attributed to the differences in their H5 sequences. Three nonconserved S6 residues have been found to affect either single-channel conductance or internal tetraethylammonium sensitivity.

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Species referenced: Xenopus
Genes referenced: btnl2