Figure 5. Mismatches in the top strand abolish HJ resolution in vitro.

In vitro activity of IntI1 on different attI substrates. (a) Gel Strand transfer test allowing the observation of HJ intermediates. Resolution of these structures through a second cleavage converts them back to the original substrate (sub). A diagram of the L and R boxes of the site is shown below its cognate gel (the rest of the site is identical to the wild type in all cases), where red bases represent changes with respect to the wild-type sequence. Crossover points in both strands are indicated with black arrows. (b) Transfer activity quantified as the amount of signal retained in the filter (HJs) over the total amount of signal. Columns represent the mean and error bars the s.d. (n=3). Transfer activity for IntI1_Y312F was undetectable in all assays. Statistical analysis was performed using Dunnett's test with the activity on the WT site as the control (*significant (α=0.05); ^**, significant (α=0.01); ND, not detected).