to promote higher activity of the protein. The transposition of a transposon often needs only three pieces: the transposon, the transposase enzyme, and the target DNA for the insertion of the transposon. This is the case with Tn5, which uses a cut-and-paste mechanism for moving around transposons. Tn5 and most other transposases contain a DDE motif, which is the active site that catalyzes the movement of the transposon. Aspartate-97, aspartate-188, and glutamate-326 make up the active site, which is a triad of acidic residues. The DDE motif is said to coordinate divalent metal ions, most often magnesium and manganese, which are important in the catalytic reaction. Because transposase is incredibly inactive, the DDE region is mutated so that the transposase becomes hyperactive and catalyzes the movement of the transposon. The glutamate is transformed into an aspartate and the two aspartates into glutamates. Through this mutation, the study of Tn5 becomes possible, but some steps in the catalytic process are lost as a result. There are several steps which catalyze the movement of the transposon, including Tnp binding, synapsis (the creation of a synaptic complex), cleavage, target capture, and strand transfer. Transposase then binds to the DNA strand and creates a clamp over the transposon end of the DNA and inserts into the active site. Once the transposase binds to the transposon, it produces a synaptic complex in which two transposases are bound in a cis/trans relationship with the transposon. In cleavage, the magnesium ions activate oxygen from water molecules and expose them to nucleophilic attack. This allows the water molecules to nick the 3' strands on both ends and create a hairpin formation, which separates the transposon from the donor DNA. Next, the transposase moves the transposon to a suitable location. Not much is known about the target capture, although there is a sequence bias which has not yet been determined. After target capture, the transposase attacks the target DNA nine base pairs apart, resulting in the integration of the transposon into the target DNA. As mentioned before, due to the mutations of the DDE, some steps of the process are lost—for example, when this experiment is performed in vitro, and SDS heat treatment denatures the transposase. However, it is still uncertain what happens to the transposase in vivo. The study of transposase Tn5 is of general importance because of its similarities to HIV-1 and other retroviral diseases. By studying