A structural model for facultative anion channels in an oligomeric membrane protein: the yeast TRK (K+) system

Juan Pablo Pardo, Martin González-Andrade, Kenneth Allen, Teruo Kuroda, Clifford L. Slayman, Alberto Rivetta

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3 Citations (Scopus)

Abstract

TRK transporters, a class of proteins which generally carry out the bulk of K+ accumulation in plants, fungi, and bacteria, mediate ion currents driven by the large membrane voltages (−150 to −250 mV) common to non-animal cells. Bacterial TRK proteins resemble K+ channels in their primary sequence, crystallize as membrane dimers having intramolecular K+-channel-like folding, and complex with a cytoplasmic collar formed of four RCK domains (Nature 471:336, 2011; Ibid 496:324, 2013). Fungal TRK proteins appear simpler in form than the bacterial members, but do possess two special features: a large built-in regulatory domain, and a highly conserved pair of transmembrane helices (TM7 and TM8, ahead of the C-terminus), which were postulated to facilitate intramembranal oligomerization (Biophys. J. 77:789, 1999; FEMS Yeast Res. 9:278, 2009). A surprising associated functional process in the fungal proteins which have been explored (Saccharomyces, Candida, and Neurospora) is facilitation of channel-like chloride efflux. That process is suppressed by osmoprotective agents, appears to involve hydrophobic gating, and strongly resembles conduction by Cys-loop ligand-gated anion channels. And it leads to a rather general hypothesis: that the thermodynamic tendency for hydrophobic or amphipathic transmembrane helices to self-organize into oligomers can create novel ionic pathways through biological membranes: fundamental hydrophobic nanopores, pathways of low selectivity governed by the chaotropic behavior of individual ionic species and under the strong influence of membrane voltage.

Original languageEnglish
Pages (from-to)2447-2460
Number of pages14
JournalPflugers Archiv European Journal of Physiology
Volume467
Issue number12
DOIs
Publication statusPublished - Dec 1 2015

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Keywords

  • Chaotropic anions
  • Compatible solutes
  • Ligand-gated channels
  • Microbial chloride efflux
  • TRK-potassium transporters

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Physiology (medical)

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