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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).

References associated with 1.A.116 family:

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. 16904148