Molecular studies of the severe acute repiratory syndrome coronavirus envelope protein

Abstract

Viorporin is a group of virus encoded small hydrophobic proteins which can form ion channel in host cell membrane and enhance membrane permeability to help virus uncoating, replication and release. In this study, we demonstrate that the envelope (E) protein (76 aa in length) of SARS-CoV possessed viroporin activities. The expression of SARS-CoV E protein in E. coli cells lead to the arrest of bacterial growth and cell permeabilization to hygromycin B and ONPG. Mammalian cells were also readily permeabilized to hygromycin B by the expression of E protein. Further studies demonstrated that this protein was an integral membrane protein and mainly located to the perinuclear region and could form dimers, trimers, tetramers, and pentamers. The transmembrane domain (9-37 aa) was confirmed to be essential for the membrane-permeabilizing activity. In mammalian cells, E protein was found to be palmitoylated on cysteine 40, 43, 44, removal of them rendered no effect on the ion channel activity. N-linked glycosylation was also found on asparagine 66, which also didn’t play a role in the E protein viroporin activity. It suggests the N-terminal transmembrane domain of E protein was sufficient to oligomerize to form ion channels in mammalian cells.