High-level chromosomally mediated tetracycline resistance in Neisseria gonorrhoeae results from a point mutation in the rpsJ gene encoding ribosomal protein S10 in combination with the mtrR and penB resistance determinants
High-level chromosomally mediated tetracycline resistance in Neisseria gonorrhoeae results from a point mutation in the rpsJ gene encoding ribosomal protein S10 in combination with the mtrR and penB resistance determinants
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DOI：
10.1128/aac.49.10.4327-4334.2005
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发表时间：
2005-10-01
影响因子：
4.9
通讯作者：
Nicholas, RA
中科院分区：
文献类型：
--
作者：
Hu, M;Nandi, S;Nicholas, RA
淋病奈瑟菌通过两种主要机制对四环素产生耐药性：质粒编码的 TetM 蛋白的表达和内源基因的突变（染色体介导的耐药性）。 Sparling 及其同事的早期研究（P. F. Sparling F. A. J. Sarubbi 和 E. Blackman, J. Bacteriol. 124:740-749, 1975）证明，三个基因参与高水平染色体介导的四环素耐药性（四环素的 MIC >= 2 μ g/ml）：ery-2（现在称为 mtrR）、penB 和 tet-2。虽然前两个基因的身份已知，但 tet-2 基因尚未确定。我们从四环素抗性临床分离淋病奈瑟菌 FA6140 中克隆了赋予四环素抗性的 tet-2 基因，并表明抗性是由于编码核糖体蛋白 S10 的 rpsJ 基因 (rpsJ1) 中的单点突变（Val-57 至 Met）所致。此外，在六种不同的四环素耐药临床分离株中发现了相同的突变，其中四环素的 MIC ≥ 2 μg/ml。 Val-57 密码子的位点饱和诱变鉴定出另外两种氨基酸（Leu 和 Gin），它们赋予与 Met-57 突变相同水平的抗性。该突变映射到 S10 中环的顶点，该顶点靠近嗜热栖热菌 30S 核糖体亚基结构中的氨酰基-tRNA 位点，而相当于嗜热栖热菌 S10 中 Val-57 的残基 Lys-55 位于结合四环素的 8 至 9 A 范围内。这些数据表明，大的不带电荷的氨基酸改变了四环素结合位点附近的rRNA结构，导致抗生素的亲和力降低。
Neisseria gonorrhoeae becomes resistant to tetracycline by two major mechanisms: expression of a plasmid-encoded TetM protein and mutations in endogenous genes (chromosomally mediated resistance). Early studies by Sparling and colleagues (P. F. Sparling F. A. J. Sarubbi, and E. Blackman, J. Bacteriol. 124:740-749, 1975) demonstrated that three genes were involved in high-level chromosomally mediated tetracycline resistance (MIC of tetracycline >= 2 mu g/ml): ery-2 (now referred to as mtrR), penB, and tet-2. While the identities of the first two genes are known, the tet-2 gene has not been identified. We cloned the tet-2 gene, which confers tetracycline resistance, from tetracycline-resistant clinical isolate N. gonorrhoeae FA6140 and show that resistance is due to a single point mutation (Val-57 to Met) in the rpsJ gene (rpsJ1) encoding ribosomal protein S10. Moreover, the identical mutation was found in six distinct tetracycline-resistant clinical isolates in which the MIC of tetracycline was >= 2 mu g/ml. Site-saturation mutagenesis of the codon for Val-57 identified two other amino acids (Leu and Gin) that conferred identical levels of resistance as the Met-57 mutation. The mutation maps to the vertex of a loop in S10 that is near the aminoacyl-tRNA site in the structure of the 30S ribosomal subunit from Thermus thermophilus, and the residue equivalent to Val-57 in T. thermophilus S10, Lys-55, is within 8 to 9 A of bound tetracycline. These data suggest that large noncharged amino acids alter the rRNA structure near the tetracycline-binding site, leading to a lower affinity of the antibiotic.