The glycoprotein 3 (GP3) of type II porcine reproductive and respiratory syndrome virus has the characteristic domains of a membrane protein. However, this protein has been reported to be retained in the endoplasmic reticulum (ER) rather than transported to the plasma membrane of the cell. In this study, we performed confocal laser scanning microscopy analysis of variants of GP3 and found that the signal sequence of the GP3 led to confinement of GP3 in the ER, while the functional ortransmembrane domain did not affect its localization. Based on these results, we concluded that the signal sequence of GP3 contains the ER retention signal, which might play an important role in assembly of viral proteins.
Keywords: endoplasmic reticulum; glycoprotein 3; porcine reproductive and respiratory syndrome virus; retention signal; signal sequence.