FIG. 4.
Both arms of the attP site contribute to attP function in the attP × attB integrative recombination reaction. Plasmids carrying various portions of attP or attR were electroporated into host strain DZ1::pAY1305, and the efficiencies with which they gave rise to Kmr recombinants were determined. The coordinates of Mx8 DNA inserts in Kmr plasmids with portions of attP (or attR) are shown on the top left, numbered as in GenBank accession no. U64984 (29). The extents of DNA inserts in the plasmids are represented as horizontal lines. All of the plasmids include the common core (filled boxes), and all but two of the plasmids carry the tMx8 terminator (open boxes). Attachment sites in these plasmids carry various combinations of the left (P) and right (P′) arms of attP, a deletion of the left arm of attP that retains the tMx8 terminator (T), the right (B′) arm of attB1 (hatched box), and/or vector sequences (V or V′) flanking the common core. Efficiencies of integration (EOI) are the average frequencies of Kmr Spr Smr recombinants recovered per microgram of plasmid DNA divided by the average frequencies of Kmr recombinants obtained from parallel electroporations of int-attP+ plasmid pAY721 and represent the average determinations from at least three independent experiments.