The M2 Proton Channels of Influenza A and B Viruses

Influenza A virus and influenza B virus are two different enveloped, negative stranded RNA viruses that cause epidemic infections. The virion (virus particle) of each virus contains a small integral membrane protein (A/M2 and BM2, respectively) that functions as a proton channel and is essential to viral replication. These proton channels are of interest because they are among the smallest bona fide ion channel proteins (with the properties of ion selectivity and activation), and they succeed in accomplishing the same function with only a meager similarity in primary amino acid sequence.