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Hybrid molecular structure of the giant protease tripeptidyl peptidase II

Crystal K Chuang1, Beate Rockel, Gönül Seyit

  • 1Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.

Nature Structural & Molecular Biology
|August 3, 2010
PubMed

Insights

The structure of the large enzyme Tripeptidyl peptidase II (TPP II) was determined, revealing compartmentalized active sites. This structure suggests a molecular ruler mechanism and a model for TPP II activation.

Area of Science:

  • Proteomics
  • Structural Biology
  • Enzymology

Background:

  • Tripeptidyl peptidase II (TPP II) is a large eukaryotic protease.
  • It functions downstream of the 26S proteasome, cleaving tripeptides from peptide N-termini.
  • TPP II is implicated in various cellular processes.

Purpose of the Study:

  • To determine the structure of Drosophila TPP II.
  • To elucidate the mechanism of TPP II activation and function.

Main Methods:

  • Hybrid approach combining X-ray crystallography and single-particle cryo-electron microscopy.
  • Structure determination of the TPP II dimer via X-ray crystallography.
  • Docking the dimer structure into the holocomplex cryo-EM map.

Main Results:

  • Revealed compartmentalization of active sites within chambers.
  • Suggested a molecular ruler mechanism for determining cleavage product size.
  • Proposed a model for TPP II activation involving loop relocation and active site serine repositioning.

Conclusions:

  • The structure provides insights into TPP II's mechanism of action and regulation.
  • Active site sequestration and holocomplex assembly are linked to activation.
  • The findings contribute to understanding proteasome-associated protein degradation pathways.

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