1.A.116.  The Pore-forming Porcine Reproductive and Respiratory Syndrome Virus Viroporin (PRRSV) Family

The small envelope (E) protein of porcine reproductive and respiratory syndrome virus (PRRSV) is a hydrophobic 73 amino acid protein encoded in the internal open reading frame (ORF) of the bicistronic mRNA2. E gene expression was blocked in a full-length infectious clone by mutating the ATG translational initiation codon to GTG, such that the full-length mutant genomic clone was unable to synthesize the E protein (Lee and Yoo 2006). An E gene knocked-out genomic clone showed the absence of virus infectivity. The E protein is essential for PRRSV infection but dispensable for virion assembly. Electron microscopy suggested that the P129-DeltaE virions assembled in the absence of E had a similar appearance to the wild-type particles. E protein-negative, non-infectious P129-DeltaE virus particles were able to enter cells, but further steps of replication were interrupted. The entry of PRRSV had been suggested to be via receptor-mediated endocytosis, and lysomotropic basic compounds and known ion-channel blocking agents both inhibited PRRSV replication effectively during the uncoating process. The expression of E protein in E. coli arrested growth and increased membrane permeability. Cross-linking experiments in cells infected with PRRSV or transfected with E gene showed that the E protein was able to form homo-oligomers. Thus, the PRRSV E protein is likely an ion-channel protein embedded in the viral envelope that facilitates uncoating of the virus and releases of the genome into the cell cytoplasm (Lee and Yoo 2006).

This family belongs to the Viroporin-3.



Lee, C. and D. Yoo. (2006). The small envelope protein of porcine reproductive and respiratory syndrome virus possesses ion channel protein-like properties. Virology 355: 30-43.


TC#NameOrganismal TypeExample

Pore-forming envelope viroporin protein, GP2b, of 70 aas and 1 (or 2) TMSs.  See family description for deetails (Lee and Yoo 2006).

Viroporin of Porcine reproductive and respiratory syndrome virus (PRRSV)


E (envelope) protein of 80 aas and 1 TMS.

E protein of Kibale red colobus virus 1


ORF2b of 70 aas and 1 TMS

ORF2b of Rodent arterivirus


E protein of 74 aas and 1 TMS

E protein of African pouched rat arterivirus


E protein of 76 aas and 1 TM

E protein of Mikumi yellow baboon virus 1


GP2a protein of 67 aas and 1 TMS. It may function as a viroporin in the virion envelope that facilitates uncoating of the virus in order to release the genomic RNA into the cytoplasm for subsequent replication.

GP2a protein of Equine arteritis virus (strain Bucyrus) (EAV)


ORF4a of 79 aas and 1 TMS.

ORF4a of Simian hemorrhagic fever virus