A sialyltransferase adds a terminal sialic acid moiety to protein 3a with an O-linked glycosyl side chain. This glycosylated form later is associated with the virion (Oostra et al, 2006).
de Haan, CA,
de Groot, RJ,
polypeptide N-acetylgalactosaminyltransferase activity of GALNT1 [endoplasmic reticulum-Golgi intermediate compartment membrane]