Influenza C virus hemagglutinin-fusion pore-forming protein of 655 aas and 4 TMSS, one N-terminal and three C-terminal but separated by about 100 residues.  Pore formation is blocked by human interferon-induced transmembrane proteins such as IFM3 (Q01628) (Desai et al. 2014).  The only spike of influenza C virus, the hemagglutinin-esterase-fusion glycoprotein (HEF) combines receptor binding, receptor hydrolysis and membrane fusion activities in a single protein. Like other hemagglutinating glycoproteins of influenza viruses, HEF is S-acylated, but only with stearic acid at a single cysteine located at the cytosol-facing end of the transmembrane region. S-acylation is essential for replication of influenza viruses A, B and C by affecting budding and/or membrane fusion (Wang et al. 2016).