Pflügers Archiv

, Volume 451, Issue 2, pp 362–370 | Cite as

In the yeast potassium channel, Tok1p, the external ring of aspartate residues modulates both gating and conductance*

  • A. Roller
  • G. Natura
  • H. Bihler
  • C. L. Slayman
  • C. Eing
  • A. BertlEmail author
Ion Channels, Transporters


The yeast plasma-membrane potassium channel, Tok1p, is a voltage-dependent outward rectifier, the gating and steady-state conductance of which are conspicuously modulated by extracellular [K+] ([K+]o). Activation is slow at high [K+]o, showing time constants (τa) of ~90 ms when [K+]o is 150 mM (depolarizing step to +100 mV), and inactivation is weak (<30%) during sustained depolarization. Lowering [K+]o accelerates activation, increases peak current, and enhances inactivation, so that at 15 mM [K+]o τa is less than 50 ms and inactivation suppresses ~60% of peak current. Two negative residues, Asp292 and Asp426, near the mouth of the assembled channel, modulate both kinetics and conductance of the channel. Charge neutralization in the mutant Asp292Asn allows fast activation (τa~20 ms) at high [K+]o, peak currents diminishing with decreasing [K+]o, and fast, nearly complete, inactivation. The voltage dependence of τa persists in the mutant, but the [K+]o dependence almost disappears. Similar but smaller changes are seen in the Asp426Asn mutant, implying that pore geometry in the functional channel has twofold, not fourfold, symmetry.


Potassium channels TOK1 Charge ring Channel gating Saccharomyces 



The authors are indebted to Drs. T. Miosga and P. Ljungdahl for yeast strains and to Drs. Yu-Feng Zhou, Lise Heginbotham and Fred Sigworth for very helpful discussions on the manuscript. The work was supported by Grants from the Deutsche Forschungsgemeinschaft (to A.B.) and from the U.S. National Institutes of Health (GM-60696, to C.L.S.).


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • A. Roller
    • 1
  • G. Natura
    • 1
    • 4
  • H. Bihler
    • 1
    • 3
  • C. L. Slayman
    • 2
  • C. Eing
    • 1
  • A. Bertl
    • 1
    Email author
  1. 1.Botanisches Institut IUniversität KarlsruheKarlsruheGermany
  2. 2.Department of Cellular and Molecular PhysiologyYale School of MedicineNew HavenUSA
  3. 3.Department of Molecular Biophysics and BiochemistryYale UniversityNew HavenUSA
  4. 4.Physiologisches InstitutUniversität JenaJenaGermany

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