Table 1. Cytolytic activity of PLY derivatives with mutations in the monomer-monomer interface.
| Toxin | EC50 (nM) | % Native PLY activity |
|---|---|---|
| PLY | 0.013 ± 0.004 | 100.00 |
| PLYK18A | ND | ND |
| PLYR208A | 0.52 ± 0.07 | 2.50 |
| PLYN66W | 0.026 ± 0.01 | 50.00 |
| PLYS68W | 0.013 ± 0.005 | 100.00 |
| PLYN66W∙S68W | 2.03 ± 0.47 | <1.00 |
| PLYN66W∙S68W∙R208A | 2.98 ± 0.66 | <1.00 |
The mean effective concentration (EC50; the concentration of toxin required to lyse 50% of RBCs) and the standard error of the mean from a minimum of three experiments are shown for each toxin. The percentage cytolytic activity of each mutant relative to native PLY activity [(EC50 native PLY/EC50 mutant) × 100] is also shown. ND, not determined because an EC50 could not be calculated as the highest concentration of toxin did not achieve 100% hemolysis.