Figure 5.

Enzyme assays. (A) BSD activity. Crude cell extracts from 3D7 alone or 3D7 transfected parasites selected on 1 μg/ml (BS1), 2 μg/ml (BS2), or 5 μg/ml (BS5) of blasticidin S were added to substrate in the assay buffer. Samples were taken at 0, 10, 20, and 30 min after incubation. The differential UV absorbance between the substrate (blasticidin S) and the deaminated product was recorded. (B) Neomycin phosphotransferase II activity. Crude cell extracts from 3D7 alone or 3D7 transfected parasites selected on 300 μg/ml (G3) or 500 (G5) μg/ml G418 were incubated with [γ-³²P]ATP and kanamycin sulfate in the assay buffer at 37°C for 60 min. The buffer alone was used as a control.