Vpr of HIV of 96 aas and one C-terminal TMS.  Vpr forms a cation-selective ion channel within the plasma membrane. The C-terminal helix (residues 56-77) effectively forms the transmembrane region, while the N-terminal helix exhibited an amphipathic nature by associating horizontally with a single leaflet (Majumder et al. 2024).  Various oligomeric states (ranging from tetramer to heptamer) were considered to form the Vpr ion channel, and a pentamer was favored.