Related Experiment Video

Updated: Jul 16, 2025

A Purification and In Vitro Activity Assay for a pppGpp Synthetase from Clostridium difficile
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Tale of Twin Bifunctional Second Messenger (p)ppGpp Synthetases and Their Function in Mycobacteria

Shubham Kumar Sinha1, Neethu Rs1, Yogeshwar Devarakonda1

  • 1Genetics and Molecular Microbiology Laboratory, Department of Biological Sciences, Institute of Eminence, Birla Institute of Technology and Sciences-Pilani, Hyderabad campus, Hyderabad, Telangana, India, 500078.

ACS Omega
|September 18, 2023
PubMed

Insights

Mycobacterium tuberculosis survival hinges on the (p)ppGpp stress response, managed by Rel enzymes. Understanding this pathway is key to developing new tuberculosis treatments targeting persistence and drug resistance.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Tuberculosis (TB) treatment is prolonged due to Mycobacterium tuberculosis's stress response and persistence.
  • The second messenger (p)ppGpp is crucial for bacterial survival, antibiotic tolerance, and the development of multidrug resistance.
  • Mycobacteria synthesize (p)ppGpp using bifunctional enzymes: long RSH-Rel (synthetase/hydrolase) and short SAS-RelZ (synthetase/RNase HII).

Purpose of the Study:

  • To elucidate the role of (p)ppGpp metabolism in mycobacterial stress response and long-term survival.
  • To investigate the unclear mechanism of Rel enzyme activity switching between synthesis and hydrolysis.
  • To highlight the potential of (p)ppGpp metabolism as a therapeutic target for tuberculosis.

Main Methods:

  • The study discusses existing literature on (p)ppGpp metabolism in mycobacteria.
  • It reviews findings on RelMtb mutants' defects in biofilm, cell wall, and persister cell formation.
  • It examines the RNase HII function of RelZ in resolving replication-transcription conflicts.

Main Results:

  • RelMtb mutants exhibit impaired biofilm formation, cell wall integrity, and persister cell generation, with compromised survival in infection models.
  • RelZ's RNase HII activity in *M. smegmatis* is linked to resolving replication-transcription conflicts.
  • The precise regulatory mechanisms and activity switching of these enzymes remain largely undetermined.

Conclusions:

  • The (p)ppGpp stress response network is vital for *M. tuberculosis* long-term survival within the host.
  • Targeting (p)ppGpp metabolism offers a promising strategy to combat persistent infections and drug resistance in TB.
  • Further research into the regulation and function of Rel enzymes is warranted for therapeutic development.

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