Helical structure of polypeptides from the C-terminal half of HIV-1 VPR

HIV-1 viral protein R (Vpr), is a 96-residue protein with a number of functions, some of which have been localised to distinct domains in the sequence. This paper describes the solution conformation, determined by NMR, of synthetic peptides encompassing a putative transmembrane helical domain of Vpr associated with formation of cation-selective channels in lipid bilayers. Peptides Vpr^50-75 (residues 50-75 of Vpr) and Vpr^50-82 both formed α-helices, encompassing residues 53-74 and 53-78, respectively. Thus, Vpr can form a helix long enough to traverse a biological membrane. The helix has some similarities to bee venom melittin, which can also form ion channels.