Figure 4.

Effect of an R₉ tag on the cytotoxicity of wild-type ribonuclease A, its G88R variant, and Onconase. Cell proliferation was determined by incorporation of [methyl-³H]thymidine into cellular DNA after a 44-h incubation with a ribonuclease. Each data point is expressed as a percentage of a PBS control. Variants with R₉ tags are denoted with filled symbols: RNase A-R₉,•; G88R RNase A-R₉, ▪ Variants without R₉ tags are denoted with open symbols: RNase A, ○; G88R RNase A,□; ONC, ▵. IC₅₀ values are listed in Table 1.