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PemK toxin of Bacillus anthracis is a ribonuclease: an insight into its active site, structure, and function

Shivangi Agarwal1, Neeraj Kumar Mishra, Sonika Bhatnagar

  • 1Laboratory of Molecular Biology and Genetic Engineering, , School of Biotechnology, Jawaharlal Nehru University, New Delhi-110067, India.

The Journal of Biological Chemistry
|December 22, 2009
PubMed

Insights

Bacillus anthracis toxin-antitoxin (TA) modules, PemK (toxin) and PemI (antitoxin), are key to stress response. Disrupting their interaction with synthetic peptides offers a novel antibacterial strategy against anthrax.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Bacillus anthracis possesses a toxin-antitoxin (TA) system, PemI/PemK, crucial for survival.
  • The PemK toxin exhibits ribonuclease activity, targeting pyrimidine bases (C/U).

Purpose of the Study:

  • To characterize the ribonuclease activity and structural basis of PemK.
  • To investigate the interaction between PemI and PemK and their role in stress response.
  • To explore the potential of disrupting TA interaction as an antibacterial strategy.

Main Methods:

  • In silico structural modeling and site-directed mutagenesis to identify key residues for PemK activity.
  • Biochemical assays to study PemI-PemK complex formation and stability.
  • Analysis of pemI-pemK transcript levels under stress conditions.
  • In vitro evaluation of synthetic peptides designed to disrupt PemI-PemK interaction.

Main Results:

  • rPemK was confirmed as a pyrimidine-specific ribonuclease, with His-59 and Glu-78 identified as critical for its activity.
  • The PemI-PemK complex is catalytically inactive at a 1:1 molar ratio, with PemI stabilizing PemK and gaining stability itself.
  • pemI-pemK expression is upregulated under stress, leading to increased PemK and decreased PemI.
  • Synthetic peptides effectively disrupted PemI-PemK interaction in vitro at micromolar concentrations.

Conclusions:

  • The PemI-PemK TA module plays a significant role in Bacillus anthracis stress response.
  • Targeting the PemI-PemK interaction with synthetic peptides presents a promising antibacterial strategy against anthrax.

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