Transport and stability of the vaccinia virus A34 protein is affected by the A33 protein

Vaccinia virus (VACV) has two infectious forms called intracellular mature virus and extracellular enveloped virus (EEV). Two of the seven viral proteins in the EEV outer envelope, A33 and A34, are type II membrane glycoproteins that each interact with another EEV protein called B5; however, evidence for direct A33–A34 interaction is lacking. The localization and stability of A34 is affected by B5 and here data are presented showing that A34 is also affected by A33. In the absence of A33, just as without B5, the level, localization and glycosylation profile of A34 was altered. However, the glycosylation profile of A34 without A33 is different to that observed in the absence of B5, and A34 accumulates in the Golgi apparatus rather than in the endoplasmic reticulum. Thus, A34 requires more than one other EEV protein for its processing and cellular transport.