FIG. 4.

Influence of intracellular NP levels on CAT activity. BHK-21 cells were seeded and transfected as described for Fig. 3A and B. Total cell extracts were processed for CAT assay as described previously (5). (A) Autoradiography of the thin-layer chromatography plate. Abbreviations: O, origin of sample application; NAc, nonacetylated chloramphenicol; MAc, monoacetylated chloramphenicol. No double-acetylated form of chloramphenicol was generated. (B) Chloramphenicol conversion was quantitated by phosphorimager analysis.