Figure 7.

Model of the integron recombination molecular mechanism using an ss attC substrate folded through pairing of the imperfect palindromic sequences. Steps are identical to classical site-specific recombination steps catalyzed by other Y-recombinases, up to the HJ intermediate. Classical resolution through the A axis reverses the recombination to the original substrates, while resolution through the B axis, giving rise to covalently closed linear molecules, is abortive. The non-abortive productive resolution necessitates a replication step. Putative IntI1 binding domains and crossover positions are indicated by boxes and vertical arrows, respectively. The extent of the attI1-protected regions in methylation interference assays (Gravel et al, 1998a), corresponding to repeats DR1 and DR2, is shown by horizontal lines with empty arrowhead.