reverse transcriptase

An enzyme that creates DNA from RNA. Necessary for the function of retroviruses. A member of the more general category of enzymes called DNA polymerases.

This enzyme can be inhibited with certain nucleoside analogs, such as AZT. They resemble normal nucleosides, and are bound by reverse transcriptase. However, they cannot be incorporated into a DNA strand, so they just remain bound, effectively jamming the active site so nothing else can bind.