Matrix protein 2 (M2) of influenza A is a tetrameric type III membrane protein that functions as
a proton-selective channel. The extracellular domain (M2e) has remained nearly invariable
since the first human influenza strain was isolated in 1933. By linking a modified form of the
leucine zipper of the yeast transcription factor GCN4 to M2e, we obtained a recombinant
tetrameric protein, M2e-tGCN4. This protein mimics the quaternary structure of the
ectodomain of the natural M2 protein. M2e-tGCN4 was purified, biochemically characterized …