Hypothetical mechanism of restriction by tetherin. The cellular restriction factor tetherin can act as a bridge between two membranes. Tetherin contains a transmembrane domain at its N-terminus and is anchored to a membrane by a glycophosphatidyl linkage at its C-terminus. It also dimerizes due to a parallel coiled-coil structure between the termini of the protein. Anchorage to membranes at both ends apparently enables tetherin to “trap” virus particles, preventing their escape from the virus-producing cell. It is not known which end of the protein is embedded in the cellular membrane and which in the viral membrane. (Figure reproduced with permission from [22].)
