Specific lid-base contacts in the 26s proteasome control the conformational switching required for substrate degradation

Elife. 2019 Nov 28;8:e49806. doi: 10.7554/eLife.49806.

Abstract

The 26S proteasome is essential for proteostasis and the regulation of vital processes through ATP-dependent degradation of ubiquitinated substrates. To accomplish the multi-step degradation process, the proteasome's regulatory particle, consisting of lid and base subcomplexes, undergoes major conformational changes whose origin is unknown. Investigating the Saccharomyces cerevisiae proteasome, we found that peripheral interactions between the lid subunit Rpn5 and the base AAA+ ATPase ring are important for stabilizing the substrate-engagement-competent state and coordinating the conformational switch to processing states upon substrate engagement. Disrupting these interactions perturbs the conformational equilibrium and interferes with degradation initiation, while later processing steps remain unaffected. Similar defects in early degradation steps are observed when eliminating hydrolysis in the ATPase subunit Rpt6, whose nucleotide state seems to control proteasome conformational transitions. These results provide important insight into interaction networks that coordinate conformational changes with various stages of degradation, and how modulators of conformational equilibria may influence substrate turnover.

Keywords: 26S proteasome; AAA+ ATPase; S. cerevisiae; biochemistry; chemical biology; ubiquitin-proteasome System.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / chemistry
  • Adenosine Triphosphatases / metabolism
  • Endosomal Sorting Complexes Required for Transport / metabolism
  • Models, Molecular
  • Nucleotides / metabolism
  • Proteasome Endopeptidase Complex / chemistry*
  • Proteasome Endopeptidase Complex / metabolism*
  • Protein Conformation
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / metabolism
  • Ubiquitin / metabolism*
  • Ubiquitin-Protein Ligase Complexes / metabolism

Substances

  • Endosomal Sorting Complexes Required for Transport
  • Nucleotides
  • Rpn5 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Ubiquitin
  • Ubiquitin-Protein Ligase Complexes
  • Proteasome Endopeptidase Complex
  • ATP dependent 26S protease
  • Adenosine Triphosphatases
  • RPT6 protein, S cerevisiae
  • RSP5 protein, S cerevisiae