Supplementary Figure 6: A single transposase subunit engages both P element donor DNAs.

Left, the RNase H domain of one subunit of transposase is catalytically engaged with one P element donor DNA (red DNA). The domains are colored as in Fig. 2c. For clarity, the dimerization domain, the GBD, and the other transposase subunit are not shown. Catalytic residues are depicted in red. Right, a 90° rotated view shows the same subunit contacting the other P element donor DNA (blue DNA), through the HTH domain, a long loop in the RNase H domain, and through the CTD. This mode of engagement likely acts as a regulatory step to ensure proper assembly with both P element ends before proceeding to catalysis.