Identification of the Glycoprotein 41™ Cytoplasmic Tail Domains of Human Immunodeficiency Virus Type 1 That Interact with Pr55 Gag Particles

We investigated the protein/protein interactions that occur during human immunodeficiency virus (HIV-1) budding. We evaluated the binding to Pr55^Gag particles of peptides mapping to the cytoplasmic tail of gp41™ and of host-cell proteins, in a cell-free, in vitro assay. Host-cell proteins and irrelevant viral envelope peptides did not bind. Peptides corresponding to a large central domain of the gp41™ cytoplasmic tail (93 residues) bound to Pr55^Gag particles. This demonstrates that a Gag/Env interaction is responsible for the specific incorporation of the Env glycoprotein into nascent HIV-1 virions, and defines more accurately the gp41™ domain involved in this interaction.