The mycobacterial Mpa-proteasome unfolds and degrades pupylated substrates by engaging Pup's N-terminus

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X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050
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X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050

Published on: May 13, 2020

Frank Striebel1, Moritz Hunkeler, Heike Summer

  • 1Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland.

The EMBO Journal
|March 6, 2010
PubMed

Insights

Mycobacterium tuberculosis uses a prokaryotic ubiquitin-like protein (Pup) system for proteasomal degradation. The Mpa ATPase unfolds and degrades Pup-tagged proteins, with Pup itself being degraded alongside the substrate.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Microbiology

Background:

  • Actinobacteria, including Mycobacterium tuberculosis, possess proteasomes for protein degradation.
  • Protein degradation in eukaryotes involves ubiquitination, a process analogous to pupylation in bacteria.

Purpose of the Study:

  • To reconstitute and characterize the mycobacterial proteasome system for pupylated substrates.
  • To elucidate the mechanism of substrate recruitment, unfolding, and degradation by the Mpa-proteasome complex.

Main Methods:

  • In vitro reconstitution of the Mpa-proteasome degradation system.
  • Biochemical assays to analyze substrate unfolding and degradation kinetics.
  • Structural analysis to identify key interaction domains between Pup and Mpa.

Main Results:

  • The Mpa-proteasome complex effectively unfolds and degrades Pup-tagged proteins.
  • Physical interaction between the ATPase Mpa and the proteasome is essential for degradation.
  • The N-terminal region of Pup serves as the recognition and threading determinant for substrate engagement.

Conclusions:

  • The study establishes the complete mechanism of pupylated substrate degradation in mycobacteria.
  • Pup functions dually as a recognition element for Mpa and a threading determinant for the proteasome.
  • Unlike eukaryotic ubiquitin, Pup is degraded along with the substrate, highlighting a unique bacterial system.

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