Manavathu E K, Fernandez C L, Cooperman B S, Taylor D E
Department of Medical Microbiology, University of Alberta, Edmonton, Canada.
Antimicrob Agents Chemother. 1990 Jan;34(1):71-7. doi: 10.1128/AAC.34.1.71.
The mechanism of resistance to tetracycline in Escherichia coli mediated by the Campylobacter jejuni-derived resistance determinant Tet(O) was investigated. The cloned Tet(O) protein had no detectable effect on the intracellular accumulation of tetracycline. The presence of Tet(O) markedly diminished the inhibitory effect of tetracycline on protein synthesis both in vivo and in vitro. Ribosomes prepared from tetracycline-resistant and susceptible E. coli cells bound almost identical amounts of radiolabeled tetracycline. Thus, a reduction in the binding of the antibiotic to its target site on the ribosome is not the primary mechanism of resistance. Poly(U)-directed polyphenylalanine synthesis revealed that an S-100 fraction prepared from tetracycline-resistant cells made the ribosomes prepared from susceptible cells considerably more resistant to the inhibitory action of tetracycline. The N-terminal portion (1 to 150 residues) of Tet(O) is highly homologous to the GTP-binding domain of elongation factor Tu and to elongation factor G, indicating that the Tet(O) protein has the potential to bind GTP. These data suggest that the Tet(O) protein could function either as a tetracycline-resistant analog of this elongation factor(s) or by modifying the target sites on the ribosomes in a catalytic fashion.
研究了空肠弯曲菌来源的耐药决定子Tet(O)介导的大肠杆菌对四环素的耐药机制。克隆的Tet(O)蛋白对四环素的细胞内积累没有可检测到的影响。Tet(O)的存在显著降低了四环素在体内和体外对蛋白质合成的抑制作用。从耐四环素和敏感的大肠杆菌细胞制备的核糖体结合几乎相同量的放射性标记四环素。因此，抗生素与其在核糖体上的靶位点结合减少不是耐药的主要机制。聚(U)指导的聚苯丙氨酸合成表明，从耐四环素细胞制备的S-100组分使从敏感细胞制备的核糖体对四环素的抑制作用具有更高的抗性。Tet(O)的N端部分（1至150个残基）与延伸因子Tu的GTP结合结构域和延伸因子G高度同源，表明Tet(O)蛋白具有结合GTP的潜力。这些数据表明，Tet(O)蛋白可以作为这种延伸因子的耐四环素类似物发挥作用，或者以催化方式修饰核糖体上的靶位点。
