FIG. 7.

Proposed pathway(s) for assembly of the Mos1 synaptic complex. First, a single Tnp molecule binds to the ITR at either half-site (SEC1). A second Tnp is then recruited to form uncleaved cis-SEC2. Two alternative pathways are then proposed for the formation of the target capture complex (TCC). In pathway 1, a conformational change may take place, allowing the formation of trans-SEC2 and the beginning of cleavages. The second ITR is then recruited to form PEC1, and finally two other Tnp molecules are included in the complex to form PEC2. In pathway 2, direct dimerization of cis-SEC2 may allow PEC2 to form and cleavages to take place. In both cases, the TCC contains a Tnp tetramer; two of these Tnp's are bound to the ITR, while the other two are disengaged from the ITR in order to capture the target. Monomers of Tnp are ringed. Double-stranded ITR are shown in gray. The TA dinucleotide flanking the ITR is shown. Flanking DNA is indicated by plain black lines for uncleaved strands and plain gray lines for strands undergoing cleavage.