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

Abstract

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 (Vpu1-32-W23L, Vpu 1-32-R31V, Vpu1-32-S24L) have been synthesized and reconstituted into artificial lipid bilayers. All peptides show channel activity with a main conductance level of around 20 pS. Vpu1-32-W23L has a considerable flickering pattern in the recordings and longer open times than Vpu1-32. Whilst recordings for Vpu1-32-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 Vpu1-32-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. © 2007 Wiley-Liss, Inc.