FIG 6.

The sequence of the LME-1 att site contributes to its low level of excision, which increases upon Lpg1867 (XerL) overexpression. (A) Comparison of the wild-type dif site in strain Murcia-4983 and the sequences flanking LME-1 resulting from att site duplication upon integration into the chromosome. The upstream copy of the dif site remains intact, but the downstream copy has three nucleotide differences (pink letters). These differences are within the inverted repeat regions of the dif site (denoted by the gray arrows), which presumably contain binding sites for Lpg1867 (XerL). (B) A kanamycin-resistance reporter cassette flanked by a wild-type dif site upstream and the indicated sequence downstream was introduced into the Lp02 Δlpg1867 strain. Excision of the reporter (indicating recombination between the two flanking sites) was quantified by plating on selective and nonselective media after transformation with empty vector or a plasmid expressing Lpg1867.