Figure 4.

Analysis of the effect of adding TrpRS to the cell culture medium on [³H]Trp uptake into HeLa cells. A, [³H]Trp uptake into HeLa cells. Data are expressed as [³H]Trp uptake relative to that of the none control. All data are expressed as mean ± S.D. of at least four independent experiments. **, p < 0.01; *, p < 0.05 versus the none control. B, SDS-PAGE of purified His₆-tagged B. subtilis TrpRS protein (the predicted molecular size 38 kDa). The sample was analyzed on 12.0% SDS-polyacrylamide gels and stained with Coomassie Brilliant Blue. The sizes in kilodaltons of molecular markers are indicated at the left.