Vpu, an integral membrane protein encoded in HIV-1, is implicated in the release of new virus particles from infected cells, presumably mediated by ion channel activity of homo-oligomeric Vpu bundles.

Reconstitution of both full length Vpu_1-81 and a short, the transmembrane (TM) domain comprising peptide Vpu_1-32 into bilayers under a constant electric field results in an asymmetric orientation of those channels. For both cases, channel activity with similar kinetics is observed. Channels can open and remain open within a broad series of conductance states even if a small or no electric potential is applied.

The mean open time for Vpu peptide channels is voltage-independent. The rate of channel opening shows a biphasic voltage activation, implicating that the gating is influenced by the interaction of the dipole moments of the TM helices with an electric field.

Key words: Vpu; HIV-1; Membrane proteins; Ion channels; and Gating.