Figure 4

Schematic representations of possible direct tethering modes. (A) Tethering by interaction via the ectodomains of Tetherin dimers. One Tetherin molecule is inserted into the virus while the other is anchored into the cellular membrane. (B) Tethering by incorporation of one of the molecule anchors in the virus and the other in the cellular membrane. Different options are shown, including GPI anchors or transmembrane domains of parallel Tetherin homodimers incorporated into a virion and (C) both type of anchors from an antiparallel tetherin homodimer incorporated into virion. The fact that deleting either the GPI anchor or the TM domain prevents the restriction suggests that either configuration A and C are not important contributors of the tethering process or that a single tethering domain is not sufficient to retain virions at the cell surface. Indeed, it is also conceivable that all these potential configurations may contribute to the restrictive activity albeit to different extent.