Identification of the pore-lining residues of the BM2 ion channel protein of influenza B virus

Chunlong Ma, Cinque S. Soto, Yuki Ohigashi, Albert Taylor, Vasilios Bournas, Brett Glawe, Maria K. Udo, William F. DeGrado, Robert A. Lamb, Lawrence H. Pinto

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45 Scopus citations


The influenza B virus BM2 proton-selective ion channel is essential for virus uncoating, a process that occurs in the acidic environment of the endosome. The BM2 channel causes acidification of the interior of the virus particle, which results in dissociation of the viral membrane protein from the ribonucleoprotein core. The BM2 protein is similar to the A/M2 protein ion channel of influenza A virus (A/M2) in that it contains an HXXXW motif. Unlike the A/M2 protein, the BM2 protein is not inhibited by the antiviral drug amantadine. We used mutagenesis to ascertain the pore-lining residues of the BM2 ion channel. The specific activity (relative to wild type), reversal voltage, and susceptibility to modification by (2-aminoethyl)-methane thiosulfonate and N-ethylmaleimide of cysteine mutant proteins were measured in oocytes. It was found that mutation of transmembrane domain residues Ser9, Ser 12, Phe13, Ser16, His19, and Trp23 to cysteine were most disruptive for ion channel function. These cysteine mutants were also most susceptible to (2-aminoethyl)-methane thiosulfonate and N-ethylmaleimide modification. Furthermore, considerable amounts of dimer were formed in the absence of oxidative reagents when cysteine was introduced at positions Ser9, Ser12, Ser16, or Trp23. Based on these experimental data, a BM2 transmembrane domain model is proposed. The presence of polar residues in the pore is a probable explanation for the amantadine insensitivity of the BM2 protein and suggests that related but more polar compounds might serve as useful inhibitors of the protein.

Original languageEnglish (US)
Pages (from-to)15921-15931
Number of pages11
JournalJournal of Biological Chemistry
Issue number23
StatePublished - Jun 6 2008

ASJC Scopus subject areas

  • Molecular Biology
  • Biochemistry
  • Cell Biology


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