Fig. 4

Assaying three phage integrases in S. cerevisiae using single target sites. a The assay for site specific recombination using single sites integrated into the LEU2 locus. Recombinants were assayed by uptake of the LEU2 gene and loss of the URA3 gene. b The assay for homologous recombination at LEU2. There was a total of 60 bp of homology with the LEU2 locus at either end of the HIS3 gene. c A summary of the activities of the optimally active forms of the ϕBT1, ϕC31 and BxB1 integrases according to their respective rank orders compared with the results of the homologous recombination assay carried out in the same experiment. All assays were carried out four times with the mean and standard deviations indicated