Influenza a virus PB1-F2 protein.

PB1-F2 protein (PB1-F2) is encoded by the alternative (+1) ORF in the PB1 gene of influenza A viruses (IAVs). This protein has a number of unique features, namely its absence from some animal IAV isolates, variable expression in individual infected cells, rapid proteasome-dependent degradation, mitochondrial localization, and apoptotic or pro-apoptotic properties. Localization of PB1-F2 to mitochondria is mediated via C-terminal basic amphipathic alpha-helix. PB1-F2 affects apoptosis and may contribute to the pathogenicity and lethality of IAVs. Sequence analysis showed that, in addition to the strains with an ORF for full-length PB1-F2, there are some with an ORF for different truncated forms of PB1-F2. Several other viruses encode proteins with structure and function similar to PB1-F2 of IAVs.