期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 105, 期 15, 页码 5885-5890出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0711949105
关键词
antitoxin; hygromycin B; bacteriophage P1; 16S rRNA; postsegregational killing
资金
- NIGMS NIH HHS [U54 GM74958, U54 GM074958] Funding Source: Medline
Bacterial toxin-antitoxin (TA) systems (or addiction modules) typically facilitate cell survival during intervals of stress by inducing a state of reversible growth arrest. However, upon prolonged stress, TA toxin action leads to cell death. TA systems have also been implicated in several clinically important phenomena: biofilm formation, bacteria[ persistence during antibiotic treatment, and bacterial pathogenesis. TA systems harbored by pathogens also serve as attractive antibiotic targets. To date, the mechanism of action of the majority of known TA toxins has not yet been elucidated. We determined the mode of action of the Doc toxin of the Phd-Doc TA system. Doc expression resulted in rapid cell growth arrest and marked inhibition of translation without significant perturbation of transcription or replication. However, Doc did not cleave mRNA as do other addiction-module toxins whose activities result in translation inhibition. Instead, Doc induction mimicked the effects of treatment with the aminoglycoside antibiotic hygromycin B (HygB): Both Doc and HygB interacted with 30S ribosomal subunits, stabilized polysomes, and resulted in a significant increase in mRNA half-life. HygB also competed with ribosome-bound Doc, whereas HygB-resistant mutants suppressed Doc toxicity, suggesting that the Doc-binding site includes that of HygB (i.e., helix 44 region of 16S rRNA containing the A, P, and E sites). Overall, our results illuminate an intracellular target and mechanism of TA toxin action drawn from aminoglycoside antibiotics: Doc toxicity is the result of inhibition of translation elongation, possibly at the translocation step, through its interaction with the 30S ribosomal subunit.
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