Reduced voltage sensitivity in a K+-channel voltage sensor by electric field remodeling

Vivian González-Pérez, Katherine Stack, Katica Boric, David Naranjo

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Propagation of the nerve impulse relies on the extreme voltage sensitivity of Na+ and K+ channels. The transmembrane movement of four arginine residues, located at the fourth transmembrane segment (S4), in each of their four voltage-sensing domains is mostly responsible for the translocation of 12 to 13 eo across the transmembrane electric field. Inserting additional positively charged residues between the voltage-sensing arginines in S4 would, in principle, increase voltage sensitivity. Here we show that either positively or negatively charged residues added between the two most external sensing arginines of S4 decreased voltage sensitivity of a Shaker voltage-gated K+-channel by up to ≈50%. The replacement of Val363 with a charged residue displaced inwardly the external boundaries of the electric field by at least 6 å, leaving the most external arginine of S4 constitutively exposed to the extracellular space and permanently excluded from the electric field. Both the physical trajectory of S4 and its electromechanical coupling to open the pore gate seemed unchanged. We propose that the separation between the first two sensing charges at resting is comparable to the thickness of the low dielectric transmembrane barrier they must cross. Thus, at most a single sensing arginine side chain could be found within the field. The conserved hydrophobic nature of the residues located between the voltage-sensing arginines in S4 may shape the electric field geometry for optimal voltage sensitivity in voltage-gated ion channels.

Original languageEnglish
Pages (from-to)5178-5183
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume107
Issue number11
DOIs
StatePublished - Mar 16 2010
Externally publishedYes

Keywords

  • Action potential
  • Charge hydration
  • Cysteine accessibility
  • Limiting slope
  • Shaker

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