Simulation of the HIV-1 Vpu Transmembrane Domain As a Pentameric Bundle

The transmembrane domain of oligomeric protein Vpu encoded by HIV-1 has been studied by means of a molecular dynamics simulation. A pentameric bundle of unconstrained helices (residues 6-28 of Vpu) with a water filled pore was initially assembled in a membrane mimetic octane/water system. This system was simulated, using the CHARMm19 and OPLS united atom force fields with no constraints at a temperature of 300 K and a pressure of 1 atm. For these forcefields and the initial conditions tested, the oligomeric bundle expelled most of the pore water molecules. The resulting bundle and residual waters adopt a conical structural motif with some resemblance to a potassium channel.