Comparison of kinetics of active tetracycline uptake and active tetracycline efflux in sensitive and plasmid RP4-containing Pseudomonas putida.
Membrane vesicles prepared from tetracycline-sensitive cells of Pseudomonas putida took up tetracycline by an active transport system with an apparent Km of 2.5 mM and a Vmax of 50 nmol min-1 mg protein-1. In contrast, resistance determinant RP4-containing P. putida had an active high-affinity efflux system for tetracycline with a Km of 2.0 to 3.54 microM and a Vmax of 0.15 nmol min-1 mg protein-1. Thus, the efflux system of tetracycline-resistant P. putida(RP4) had an average of 1,000-fold greater affinity for tetracycline than the influx system of tetracycline-sensitive cells. From these results, it is clear that a major mechanism of tetracycline resistance in RP4-containing P. putida is an active tetracycline efflux mechanism. There was also evidence for a second tetracycline efflux system with low affinity for tetracycline n P. putida(RP4). This efflux system had a Km of 0.25 mM and a Vmax of 1.45 nmol min-1 protein-1. Whether this low-affinity efflux system was also present in tetracycline-sensitive P. putida could not be discerned from these experiments.
D001693:Biological Transport, Active; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D007700:Kinetics; D011549:Pseudomonas / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011815:R Factors; D013752:Tetracycline / Q000378:metabolism* / Q000494:pharmacology
D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D013752:Tetracycline