Viral ion channels (viroporins) are known since at least 1992, when the M2 channel of influenza A virus has been discovered. These ion channels exist in a form of homotetra-(e.g. the M2 channel) or homopentamers (e.g. coronavirus E channel); each subunit is 50-120 aminoacids long and has at least one transmembrane domain (TMD). The pore formed by the transmembrane domains of the oligomer acts as an ion channel. It is speculated that viroporins initiate a leakage in host cell membranes, which alters the tans-membrane potential and serves as a marker of viral infection . SARS coronaviruses were found to have at least three types of ion channels: E and 8a (both with single TMD, forming pentameric assemblies), and 3a with three TMD . Both proteins E and 3a possess PDZ domainbinding motif (PBM). In the protein E it is the last four aminoacids in the C-terminus (DLLV, Table ). The PBM of E protein was found to be directly involved in SARS-CoV pathogenesis by binding the host's syntenin protein resulting in overexpression of inflammatory cytokines contributing to the socalled "cytokine storm" . Further to that, SARS-CoV E channel can be embedded into the ERGIC/Golgi membranes and facilitate Ca 2+ transport resulting in the activation of the NLRP3 inflammasome followed by an overproduction of interleukin 1β . In the lifecycle of coronaviruses, E protein was found to be involved in morphogenesis and viral assembly, and was essential for the virus fitness . This is evidenced by the experiment in which mutant SARS-CoV viruses with inactive E protein (caused by N15A or V25F mutation) were prone to revert the protein to its active state, both in cell culture and in infected mice. Lack of E viroporin activity led to a significant reduction in pulmonary edema in mice, resulting in much lower mortality rates . An exhaustive review of modern knowledge of molecular biology of coronavirus E proteins is given by Schoelman & Fielding .