HIV-1 reverse transcriptase enzyme. Molecular model of the transferase enzyme HIV-1 reverse transcriptase, bound to a RNA-DNA hybrid (green and blue helix). This protein is an enzyme that mediates the copying of genetic information, in this case by the human immunodeficiency virus (HIV) when infecting cells. HIV is the cause of AIDS (acquired immunodeficiency syndrome). This transferase protein consists of two single-chain polymers (red and purple), containing 560 and 440 amino acids respectively.