The active oligomeric state of the minimalistic influenza virus M2 ion channel is a tetramer

Takemasa Sakaguchi, Qiang Tu, Lawrence H. Pinto, Robert A. Lamb*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

145 Scopus citations


The influenza A virus M2 integral membrane protein is an ion channel that permits protons to enter virus particles during uncoating of virions in endosomes and also modulates the pH of the trans-Golgi network in virus- infected cells. The M2 protein is a homo-oligomer of 97 residues, and analysis by chemical cross-linking and SDS/PAGE indicates M2 forms a tetramer. However, a higher order molecular form is sometimes observed and, thus, it is necessary to determine the active form of the molecule. This was done by studying the currents of oocytes that expressed mixtures of the wild- type M2 protein (epitope tagged) and the mutant protein M2-V27S, which is resistant to the inhibitor amantadine. The composition of mixed oligomers of the two proteins expressed at the plasma membrane of individual oocytes was quantified after antibody capture of the cell surface expressed molecules and it was found that the subunits mixed freely. When the ratio of wild-type to mutant protein subunits was 0.85:0.15, the amantadine sensitivity was reduced to 50% and for a ratio of 0.71:0.29 to 20%. These results are consistent with the amantadine-resistant mutant being dominant and the oligomeric state being a tetramer.

Original languageEnglish (US)
Pages (from-to)5000-5005
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number10
StatePublished - May 13 1997


  • M protein
  • amantadine
  • channel oligomeric form
  • influenza A virus

ASJC Scopus subject areas

  • General


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