The chromosomal tetracycline resistance locus of Bacillus subtilis encodes a Na+/H+ antiporter that is physiologically important at elevated pH.
The chromosomal tetracycline resistance locus of Bacillus subtilis encodes a Na+/H+ antiporter that is physiologically important at elevated pH.
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DOI：
10.1016/s0021-9258(18)46994-3
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发表时间：
1994-11
期刊：
影响因子：
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通讯作者：
J. Cheng;A. Guffanti;T. A. Krulwich
中科院分区：
文献类型：
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作者：
J. Cheng;A. Guffanti;T. A. Krulwich
枯草芽孢杆菌的染色体 tetB(L) 基因编码一种转运蛋白，其催化 Na+/H+ 逆向转运甚至比四环素/H+ 逆向转运更活跃，如用克隆基因转化 Na+/H+ 逆向转运蛋白缺陷的大肠杆菌后膜逆向转运蛋白活性的测定所示；该转化导致 Na+ 抗性显着增加，并且可检测到对低四环素浓度的抗性。枯草芽孢杆菌染色体 tetB(L) 基因座的转位破坏导致电 Na+ 流出率降低，并揭示了该基因座在 Na+ 抗性和 pH 8.5 下 Na(+) 依赖性 pH 稳态中的生理作用。通过用表达克隆的tetB(L)基因的质粒转化来逆转突变表型。野生型中能量依赖性四环素流出率高于转座突变体，但不足以赋予抗生素抗性。 TetB(L) 还被推断具有适度的 K+ 流出能力，因为转座突变体在 pH 8.5 下 K(+) 依赖性 pH 稳态略有受损，并且在限制 K+ 浓度的 pH 7 下比野生型生长得更好。
The chromosomal tetB(L) gene of Bacillus subtilis encodes a transporter that catalyzes Na+/H+ antiport even more actively than tetracycline/H+ antiport, as shown by assays of membrane antiporter activity upon transformation of Na+/H+ antiporter-deficient Escherichia coli with the cloned gene; the transformation results in a substantial increase in Na+ resistance as well as detectable resistance to low tetracycline concentrations. Transpositional disruption of the chromosomal tetB(L) locus of B. subtilis led to reduced rates of electrogenic Na+ efflux and revealed a physiological role for this locus in Na+ resistance and Na(+)-dependent pH homeostasis at pH 8.5. The mutant phenotype was reversed by transformation with a plasmid expressing the cloned tetB(L) gene. Energy-dependent tetracycline efflux rates in the wild type were greater than in the transposition mutant but were not sufficient to confer resistance to the antibiotic. TetB(L) is also inferred to have a modest capacity for K+ efflux, since the transposition mutant is slightly impaired in K(+)-dependent pH homeostasis at pH 8.5 and grew better than the wild type at pH 7 on limiting K+ concentrations.