FIGURE 6.

Biotin interference assay of integrative recombination. Supercoiled attP sites containing a single biotin dT substitution at one of the indicated positions in the top strand (t.s.) were recombined with a radiolabeled linear attB partner, and the recombination efficiency was normalized to that of a control reaction with no substitutions (10–20% recombination efficiency). Based on the x-ray crystal structure, the biotin at -149 (^*) is predicted to interfere with the putative non-canonical Int binding in the same way that biotin at position -139 blocks Int binding at P1. Biotin dT substitutions at positions -154, -149, and -144 required changing the wild-type sequences from A, C, and A, respectively; in each case the unsubstituted control attP (wild-type (WT)) contained the identical changes.