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. 2011 Apr 29;6(4):e19537. doi: 10.1371/journal.pone.0019537

Figure 3. Selection of ZFRs to recombine casein gene sequences.

Figure 3

(A) Activity of the progenitor ZFR (ZFR300) on Z-sites with central sequences from Tn3 res site I or the casein gene intron 1. The substrate plasmids each contained two identical Z-sites as indicated above the gel lanes. The numbers below each lane represent the percentage of recombinant plasmids in the recovered DNA (see Materials and Methods). Images of the ethidium-stained gels are greyscale-inverted, and a uniform background subtraction has been applied. A representative sector of a plate from the corresponding MacConkey-galactose assay is shown above each lane. Annotation: exp, ZFR expression plasmid; nr, non-recombinant substrate plasmid; rec, recombinant (galK −) plasmid. (B) Activity of the first round mutant I77L (ZFR310) on the same substrates as in A. (C) Activity of the second round double mutant I77L E132A (ZFR320) on the same substrates as in A.