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Interference of mRNA function by sequence-specific endoribonuclease PemK
Junjie Zhang1, Yonglong Zhang, Ling Zhu
1Department of Biochemistry, Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
The Journal of Biological Chemistry
|March 17, 2004
Summary
The pemI-pemK addiction module in E. coli uses PemK toxin to inhibit protein synthesis by cleaving mRNA. PemI antitoxin neutralizes PemK, restoring protein production and maintaining plasmid stability.
Area of Science:
- Molecular Biology
- Bacteriology
- Genetics
Background:
- Programmed cell death in Escherichia coli is regulated by addiction modules.
- The pemI-pemK system on plasmid R100 is an addiction module.
- This system ensures plasmid maintenance via post-segregational killing.
Purpose of the Study:
- To investigate the mechanism of action of the PemK toxin and PemI antitoxin.
- To determine how the pemI-pemK addiction module inhibits protein synthesis.
- To characterize PemK as an endoribonuclease.
Main Methods:
- Purification of PemK and PemI proteins.
- In vitro cell-free protein synthesis assays.
- RNA cleavage assays to identify PemK's target sequences.
Main Results:
- Purified PemK inhibits protein synthesis in a cell-free system.
- PemI counteracts PemK's inhibitory effect, resuming protein synthesis.
- PemK acts as a sequence-specific endoribonuclease, cleaving mRNA at "UAH" sequences, preferentially near A residues.
Conclusions:
- PemK is a novel endoribonuclease that targets cellular mRNAs.
- PemI functions as an antitoxin by inhibiting PemK's nuclease activity.
- PemK and its homologs represent a new family of endoribonucleases impacting mRNA function across bacteria.