The Matrix-2 (M2) protein is a proton-selective viroporin, integral in the viral envelope of the influenza A virus. The channel itself is a homotetramer (consists of four identical M2 units), where the units are helices stabilized by two disulfide bonds, and is activated by low pH. The M2 protein is encoded on the seventh RNA segment together with the M1 protein. Proton conductance by the M2 protein in influenza A is essential for viral replication.
Influenza B and C viruses encode proteins with similar function dubbed "BM2" and "CM2" respectively. They share little similarity with M2 at the sequence level, despite a similar overall structure and mechanism.[1]
- ^ Pielak RM, Chou JJ (February 2011). "Influenza M2 proton channels". Biochimica et Biophysica Acta (BBA) - Biomembranes. 1808 (2): 522–9. doi:10.1016/j.bbamem.2010.04.015. PMC 3108042. PMID 20451491.