The molecular mechanism by which HIV-1 Gag proteins are targeted and transported to the plasma membrane after ribosomal synthesis is unknown. In this work, we investigated the potential interaction of p6 and Vpr with model membranes and have determined their binding constants. Plasmon waveguide resonance (PWR) experiments showed that p6 strongly interacts with membranes (K(d) approximately 40 nM), which may help explaining in part why Gag is targeted to and assembles into membranes by coating itself with lipids. Moreover, a substantial increased affinity of Vpr for p6 was observed while in a membrane environment. In order to further investigate the molecular properties behind the high affinity to model membranes, molecular dynamics simulations were carried out for p6 with a dodecylphosphocholine (DPC) micelle. The results indicate an integration route model for Vpr into virions and may help explain why previous reports failed to detect p6 in virion core preparations.