McMurry L, Petrucci R E, Levy S B
Proc Natl Acad Sci U S A. 1980 Jul;77(7):3974-7. doi: 10.1073/pnas.77.7.3974.
Tetracycline resistance encoded by four genetically different determinants residing on plasmids in Escherichia coli was shown to be associated in each case with an energy-dependent decrease in accumulation of the antibiotic in whole cells in which resistance had been induced. The different class determinants examined were those on plasmids RP1 (class A), R222 (class B), R144 (class C), and RA1 (class D). This decrease in accumulation was attributable to an active efflux, because everted (inside-out) membrane vesicles made from tetracycline-induced E. coli cells containing any one of the four plasmids were shown to concentrate tetracycline by an active influx. This active uptake was not seen in inside-out vesicles from sensitive cells or uninduced R222-containing cells. In vesicles from induced R222-containing cells, the efflux appeared to be carrier-mediated with a Km of about 6 microM. These results demonstrate that active export of tetracycline is a common component of the mechanism for tetracycline resistance encoded by different plasmid-borne determinants in bacteria.
大肠杆菌中存在于质粒上的四种基因不同的决定簇所编码的四环素抗性，在每种情况下都显示与诱导产生抗性的全细胞中抗生素积累的能量依赖性减少有关。所检测的不同类别决定簇是质粒RP1（A类）、R222（B类）、R144（C类）和RA1（D类）上的那些。积累的减少归因于主动外排，因为由含有四种质粒中任何一种的四环素诱导的大肠杆菌细胞制成的外翻（内翻外）膜囊泡通过主动内流来浓缩四环素。在敏感细胞或未诱导的含R222细胞的内翻外囊泡中未观察到这种主动摄取。在含诱导型R222细胞的囊泡中，外排似乎是载体介导的，Km约为6微摩尔。这些结果表明，四环素的主动输出是细菌中不同质粒携带决定簇所编码的四环素抗性机制的一个共同组成部分。
