Biophysical characterization of Vpu from HIV‐1 suggests a channel‐pore dualism

Mehnert, T.; Routh, A.; Judge, P. J.; Lam, Y. H.; Fischer, D.; Watts, A.; Fischer, W. B.

Vpu from HIV‐1 is an 81 amino acid type I integral membrane protein which consists of a cytoplasmic and a transmembrane (TM) domain. The TM domain is known to alter membrane permeability for ions and substrates when inserted into artificial membranes. Peptides corresponding to the TM domain of Vpu (Vpu(1‐32)) and mutant peptides (Vpu(1‐32)‐W23L, Vpu(1‐32)‐R31V, Vpu(1‐32)‐S24L) have been synthesized and reconstituted into artificial lipid bilayers. All peptides show channel activity with a main conductance level of around 20 pS. Vpu(1‐32)‐W23L has a considerable flickering pattern in the recordings and longer open times than Vpu(1‐32). Whilst recordings for Vpu(1‐32)‐R31V are almost indistinguishable from those of the WT peptide, recordings for Vpu(1‐32)‐S24L do not exhibit any noticeable channel activity. Recordings of WT peptide and Vpu(1‐32)‐W23L indicate Michaelis–Menten behavior when the salt concentration is increased. Both peptide channels follow the Eisenman series I, indicative for a weak ion channel with almost pore like characteristics. Proteins 2008. © 2007 Wiley‐Liss, Inc.