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Selective degradation of ubiquitinated Sic1 by purified 26S proteasome yields active S phase cyclin-Cdk

Academic Article
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Overview

authors

  • Verma, R.
  • McDonald, H.
  • Yates III, John
  • Deshaies, R. J.

publication date

  • 2001

journal

  • Molecular Cell  Journal

abstract

  • Selective degradation of single subunits of multimeric complexes by the ubiquitin pathway underlies multiple regulatory switches, including those involving cyclins and Cdk inhibitors. The machinery that segregates ubiquitinated proteins from unmodified partners prior to degradation remains undefined. We report that ubiquitinated Sic1 (Ub-Sic1) embedded within inactive S phase cyclin-Cdk (S-Cdk) complexes was rapidly degraded by purified 26S proteasomes, yielding active S-Cdk. Mutant proteasomes that failed to degrade Ub-Sic1 activated S-Cdk only partially in an ATP-dependent manner. Whereas Ub-Sic1 was degraded within approximately 2 min, spontaneous dissociation of Ub-Sic1 from S-Cdk was approximately 200-fold slower. We propose that the 26S proteasome has the intrinsic capability to extract, unfold, and degrade ubiquitinated proteins while releasing bound partners untouched. Activation of S-Cdk reported herein represents a complete reconstitution of the regulatory switch underlying the G1/S transition in budding yeast.

subject areas

  • Adenosine Triphosphate
  • Cell Line
  • Cyclin-Dependent Kinase Inhibitor Proteins
  • Cyclin-Dependent Kinases
  • Cyclins
  • Cysteine Endopeptidases
  • Endopeptidases
  • Enzyme Activation
  • Enzyme Inhibitors
  • Fungal Proteins
  • Immunoblotting
  • Mutation
  • Peptide Hydrolases
  • Proteasome Endopeptidase Complex
  • Protein Subunits
  • S Phase
  • Saccharomyces cerevisiae Proteins
  • Saccharomycetales
  • Ubiquitins
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Identity

International Standard Serial Number (ISSN)

  • 1097-2765

Digital Object Identifier (DOI)

  • 10.1016/s1097-2765(01)00308-2

PubMed ID

  • 11545745
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Additional Document Info

start page

  • 439

end page

  • 448

volume

  • 8

issue

  • 2

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