Viroporins are a group of viral proteins that participate in viral replication cycles, including modification of membrane permeability and promotion of viral release.Although biological data have been accumulated on viroporion-like proteins of other viruses belonging to family Flaviviridae, the viroporin activity and membrane topology of p7 protein from classical swine fever virus (CSFV), a member of the genus Pestivirus of the family Flaviviridae, are largely unknown.