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. 2014 Aug 11;111(34):12366–12371. doi: 10.1073/pnas.1413007111

Fig. 4.

Fig. 4.

Confirmation of the Int bridges in complete recombination reactions. (A) Schematic of unique specificity bridging enzymes. Chimeric recombinase Crn1 (17) possesses the NTD of λ Integrase (small gold triangle), which binds to the DNA consensus sequence MRGTCACTAT, fused to the body of Cre (large gold triangle), which binds to the modified loxP (lot) site, ATAACTTCGTAGA. Crn2 possesses the NTD of AtERF (small purple box), which binds to the consensus GCC box sequence, AGAGCCGCCA, fused to the body of CreCM2 (large purple box), which binds to the lotM7 sequence, ATAACTCTATAGA. Crn3 is the same as Crn2, but the α-helix of AtERF has been replaced by a structurally analogous α-helix from λ Integrase (red triangle), which interacts with Xis (SI Text). The gold and purple color coding of the two DNA specificities is preserved in B. (B) Cartoon of the logic and possible outcomes of the experiments. In each of the excisive and integrative recombination reactions shown in Fig. 5, one of the arm-core pairs has the DNA sequences of the unique Crn2/3 specificity (purple), as indicated, whereas all of the other arm and core sites have the Crn1 specificity (gold). Recombinant product (+) is observed only when the complete and correct Int bridging pattern is achieved.