The ion channel viral protein U, Vpu of 81 aas and 1 TMS. Vpu(1-32), forms a helix bundle with characteristic open states. Different amilorides inhibit channel activity (Römer et al. 2004). The mutation A18H converts a non-specific channel to a selective proton channel that is sensitive to rimantadine (Sharma et al., 2011).  Vpu forms stable pentamers (Padhi et al. 2013).  The mechanism of Vpu, a weakly conducting cation-selective channel that assists in detachment of the virion from infected cells, has been proposed (Padhi et al. 2014).  Interactions of Vpu with host cellular constituents have been reviewed (González 2015). Vpu forms large homo aggregates of 16 or 32 subunits (Lin et al. 2016). Vpu is involved in the enhancement of virion release via formation of an ion channel. Cyclohexamethylene amiloride (Hma) inhibits ion channel activity. A putative binding site for Hma blockers in a pentameric model bundle built of parallel aligned helices of the first 32 residues of Vpu was found near Ser-23. Hma orientates along the channel axis with its alkyl ring pointing inside the pore, which leads to a blockage of the pore (Lemaitre et al. 2004).