The DDE motif. Consensus sequences are shown for the catalytic domain of two families of transposases: the Tn3 family and retroviral integrases. The DDE motif consists of three residues (Asp, Asp, and Glu, shown in red) that are generally not adjacent in the primary sequence but come together at the active site when the protein is folded. The motif is found in most transposases and integrases. Alternative residues at any position are shown above or below the line; those shown in blue (up to two at a given position) are residues found at that position in more than 75% of the enzymes of this family. Dashes indicate any amino acid residue. Two peptide segments, with the residue numbers indicated, are omitted here.