Fig. 3

Assaying activity of fourteen phage integrases in S. cerevisiae. Strains expressing containing the integrase assay plasmid (Fig. 1c) and expressing the indicated integrase were transformed with the LEU2 donor plasmid (Fig. 1b) and selected for leucine prototrophy. The number of leucine prototrophs recovered following transformation of 10⁷ cells is indicated and as the negative control shows reflects the activities of the integrases. Each integrase was assayed under four different patterns of expression with respect to the transformation. Each transformation was repeated four times with the mean and sample standard deviation indicated. The four conditions correspond to either induction or non-induction of integrase expression either before or after transformation and this is indicated by the traffic light cartoon in the top right hand corner of each part of the figure. (Non-induction (red) is when the cells are grown in the presence of Doxycycline which represses the Tet promoter and induction (green) corresponds to growth in the absence of Doxycycline). a The activity of each integrase lacking a nuclear localization signal. Integrases judged to be toxic on the basis of the analyses shown in Fig. 2 are grouped on the right hand side of the panel. b The activity of the integrases with a C-terminal nuclear localization signal and, as in A, integrases judged to be toxic on the basis of the analyses shown in Fig. 2 are grouped on the right hand side of the panel. c A summarizes the different integrases according to the rank order of the activities of their optimally active forms and whether they were toxic or not. As in A and B, integrases judged to be toxic are grouped on the right hand side of the panel