📄 Biochemical evidence for the presence of mixed membrane topologies of the severe acute respiratory syndrome coronavirus envelope protein expressed in mammalian cells

Coronavirus envelope (E) protein is a small integral membrane protein with multi-functions in virion assembly, morphogenesis and virus-host interaction. Different coronavirus E proteins share striking similarities in biochemical properties and biological functions, but seem to adopt distinct membrane topology. In this report, we study the membrane topology of the SARS-CoV E protein by immunofluorescent staining of cells differentially permeabilized with detergents and proteinase K protection assay. It was revealed that both the N- and C-termini of the SARS-CoV E protein are exposed to the cytoplasmic side of the membranes (Ncyto. Ccyto). In contrast, parallel experiments showed that the E protein from infectious bronchitis virus (IBV) spanned the membranes once, with the N-terminus exposed luminally and the C-terminus exposed cytoplasmically (Nexo(lum)Ccyto). Intriguingly, a minor proportion of the SARS-CoV E protein was found to be modified by N-linked glycosylation on Asn 66 and inserted into the membranes once with the C-terminus exposed to the luminal side. The presence of two distinct membrane topologies of the SARS-CoV E protein may provide a useful clue to the pathogenesis of SARS-CoV. © 2006 Federation of European Biochemical Societies.

keywords 🔗 bronchitis virus (233) 🔗 infectious bronchitis (235) 🔗 membrane protein (93)

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