Mechanism for proton conduction of the M2 ion channel of influenza A virus

Jorgen A. Mould, Hui Chun Li, Christine S. Dudlak, James D. Lear, Andrew Pekosz, Robert A. Lamb, Lawrence H. Pinto*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

128 Scopus citations


The M2 integral membrane protein of influenza A virus forms a proton- selective ion channel. We investigated the mechanism for proton transport of the M2 protein in Xenopus oocytes using a two-electrode voltage clamp and in CV-1 cells using the whole cell patch clamp technique. Membrane currents were recorded while manipulating the external solution to alter either the total or free proton concentration or the solvent itself. Membrane conductance decreased by ~50% when D2O replaced H2O as the solvent. From this, we conclude that hydrogen ions do not pass through M2 as hydronium ions, but instead must interact with titratable groups that line the pore of the channel. M2 currents measured in solutions of low buffer concentration (<15 mM in oocytes and <0.15 mM in CV-1 cells) were smaller than those studied in solutions of high buffer concentration. Furthermore, the reversal voltage measured in low buffer was shifted to a more negative voltage than in high buffer. Also, at a given pH, M2 current amplitude in 15 mM buffer decreased when pH-pK(a) was increased by changing the buffer pK(a). Collectively, these results demonstrate that M2 currents can be limited by external buffer capacity. The data presented in this study were also used to estimate the maximum single channel current of the M2 ion channel, which was calculated to be on the order of 1-10 fA.

Original languageEnglish (US)
Pages (from-to)8592-8599
Number of pages8
JournalJournal of Biological Chemistry
Issue number12
StatePublished - Mar 24 2000

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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