Figure 2: HIV-1 is a retrovirus that is approximately 90 – 120 nm in diameter and is enveloped by a host-derived plasma membrane. Trimeric envelope glycoproteins gp120/41 form the spikes on the virions surface and are embedded in the membrane. The cytoplasmic tail of gp41 interacts with the HIV-1 matrix protein p17. During maturation the capsid protein, p24, makes up the cone-shaped core, which contains two positive-strand RNA copies of the HIV-1 genome, the reverse transcriptase protein, as well as a number of other important host proteins.