Caption: Ribbon diagram of the crystal structure of the Tn5 transposase/DNA complex, with the short pieces of DNA from the crystal structure extended to illustrate how the ends of the transposon bound to the protein/DNA complex are part of a continuous loop. One molecule of transposase is orange and the other is yellow, with the DNA shown in purple.
Image source: University of Wisconsin-Madison.
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Caption: Schematic illustration of the mechanism of transposition catalyzed by the Tn5 transposase. In the first step, individual molecules of transposase (blue spheres) bind to specific sites at the ends of the transposon DNA (purple). In the next step, looping of the transposon DNA results in formation of a synaptic complex that brings the two ends of the transposable element close together. Once the synaptic complex has been formed, the Tn5 transposase cuts the transposon DNA away from the flanking "donor" DNA (green). After cleavage, the Tn5 transposase/DNA complex can move about freely until it encounters and binds to the "target" DNA (red). Through a process called strand transfer the transposase catalyzes insertion of the transposon DNA into the target DNA, completing the transposition process.
Image credit: © 2000 Science.
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