A new set of Mu DNA transposition intermediates: alternate pathways of target capture preceding strand transfer.

Mu DNA transposition occurs within the context of higher order nucleoprotein structures or transpososomes. We describe a new set of transpososomes in which Mu B-bound target DNA interacts non-covalently with previously characterized intermediates prior to the actual strand transfer. This interaction can occur at several points along the reaction pathway: with the LER, the Type 0 or the Type 1 complexes. The formation of these target capture complexes, which rapidly undergo the strand transfer chemistry, is the rate-limiting step in the overall reaction. These complexes provide alternate pathways to strand transfer, thereby maximizing transposition potential. This versatility is in contrast to other characterized transposons, which normally capture target DNA only at a single point in their respective reaction pathways.