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The antiphage mechanism of a widespread trypsin-MBL defense module

Pingping Huang1,2,3, Jingxian Liu1,2, Lijie Guo1,2,4

  • 1State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, China.

Nature Chemical Biology
|June 4, 2026
PubMed

Insights

A trypsin-metallo-β-lactamase (MBL) module is key in bacterial antiviral immunity. This system uses protease activation to degrade foreign DNA and prevent phage infections.

Area of Science:

  • Molecular Biology
  • Bacterial Immunity
  • Enzymology

Background:

  • Protease-mediated activation is a conserved immune mechanism.
  • Bacterial antiviral systems utilize diverse effector proteins.

Purpose of the Study:

  • To identify and characterize the trypsin-metallo-β-lactamase (MBL) module in bacterial antiviral immunity.
  • To elucidate the activation mechanism of the Hachiman-associated trypsin-MBL system.

Main Methods:

  • Cryo-electron microscopy (Cryo-EM) to determine structural details.
  • Biochemical assays to study enzyme activity and regulation.
  • In vitro studies of protease and nuclease function.

Main Results:

  • The trypsin-MBL module functions as a core effector in bacterial antiviral systems.
  • ATP binding regulates trypsin•HamAB activity; DNA binding and ATP hydrolysis activate it.
  • Activated MBL acts as a DNase, degrading foreign DNA and arresting host cell growth.
  • Cryo-EM structures reveal DNA-triggered oligomerization and activation of trypsin•HamAB.

Conclusions:

  • Proteolytic activation of a nuclease is a conserved mechanism for robust phage immunity.
  • Multilayered regulatory controls prevent self-toxicity in bacterial immune systems.
  • This study expands the understanding of immune processes regulated by proteolytic activation.

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