Structure of a typical long terminal repeat retrotransposon. Adapted from. AP:Aspartic protease; IN: integrase; LTR: long terminal repeat; PPT: polypurine tract; RH: RNase H; RT: reverse transcriptase; TSD: target site duplication. The numbers below the illustration denote typical lengths of the respective component. This example is of the copia-like superfamily, as it shows the IN-RT-RH domain order.