Full-length SARS-CoV-2 envelope protein adopts an interfacial topology in lipid bilayers

The envelope protein is essential for the replication of coronaviruses. Several structures of the envelope protein of the SARS-CoV-2 and the closely related SARS viruses are available. However, an experimental structure of the entire full-length protein in a native lipid environment has not been determined. In addition, significant structural differences exist between published models, and the conformation adopted by the C-terminal domain is only partially understood. CW-EPR power saturation and EPR lineshape analysis of 15 different labeled sites were carried out on the full-length envelope protein of SARS-CoV-2 in POPC/POPG vesicles to determine the membrane topology. In conjunction with coarse-grained molecular dynamics, the results support a model where the C-terminal domain helices as well as the N-terminal domain are in direct contact with the lipid headgroups of the ER cytoplasmic leaflet of the membrane.