Fig. 3.

Schematic representation of the HIV-1 particle and its protein and genomic RNA contents. Two copies of the viral positive strand RNA genome are packaged into the particle. Viral enzymes; reverse transcriptase (RT), integrase (IN), protease (Pr) and structural proteins; capsid (CA), nucleocapsid (NC), matrix (MA) and p6 are inside the particle together with the viral regulatory protein Vpr and the cellular protein cyclophilin. The virus is enveloped by a host cell-derived lipid membrane into which trimers of the viral transmembrane glycoprotein gp41 is inserted. Three monomers of the exterior envelope glycoprotein gp120 are noncovalently associated with gp41. Several cellular proteins are also incorporated into the viral membrane with relative abundance, including MHC class I and II molecules and intracellular adhesion molecule-1 shown here.