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Comparative Strategies for Ubiquitination Detection in Mammalian Cell Lysates Using SMAD2/SMURF2 as a Model
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Structural basis for ubiquitin recognition by the Otu1 ovarian tumor domain protein

Troy Eugene Messick1, Nathaniel Scott Russell, Ayaka Jennifer Iwata

  • 1Wistar Institute, Philadelphia, Pennsylvania 19104, USA.

The Journal of Biological Chemistry
|February 14, 2008
PubMed

Insights

Yeast Otu1, an ovarian tumor (OTU) domain protein, binds and hydrolyzes polyubiquitin chains. Structural studies reveal a novel ubiquitin recognition mode and catalytic site variation in this important deubiquitinating enzyme.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • Protein ubiquitination regulates diverse cellular processes.
  • Deubiquitinating enzymes (DUBs) reverse ubiquitination.
  • Ovarian tumor (OTU) domain proteins are a class of DUBs.

Purpose of the Study:

  • To investigate the structural and functional characteristics of yeast Otu1, an OTU domain-containing protein.
  • To elucidate the ubiquitin-binding and hydrolytic mechanisms of Otu1.
  • To understand the conservation of OTU domain catalytic mechanisms.

Main Methods:

  • Biochemical assays to assess ubiquitin chain hydrolysis.
  • Co-immunoprecipitation to study protein interactions.
  • X-ray crystallography to determine the structure of the Otu1-ubiquitin complex.
  • Site-directed mutagenesis to probe catalytic residues.

Main Results:

  • Otu1 preferentially binds and hydrolyzes Lys(48)-linked polyubiquitin chains.
  • Otu1 interacts with Cdc48, a key regulator of ER-associated degradation.
  • The crystal structure reveals a novel ubiquitin recognition mechanism and a variant papain-like catalytic site.
  • Mutagenesis studies confirm the importance of identified residues for activity.

Conclusions:

  • Yeast Otu1 functions as a specific deubiquitinating enzyme with a preference for Lys(48)-linked polyubiquitin.
  • The structural insights provide a mechanistic understanding of ubiquitin recognition and hydrolysis by OTU domain proteins.
  • Otu1's interaction with Cdc48 suggests a role in the ER-associated degradation pathway.
  • The findings offer a foundation for understanding other OTU deubiquitinating enzymes.

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