A Tetrahedral Transition State at the Active Sites of the 20S Proteasome Is Coupled to Opening of the α-Ring Channel

Research output: Contribution to journalArticle

58 Scopus citations

Abstract

Intrinsic conformational transitions contribute to the catalytic action of many enzymes. Here we use a single-molecule approach to demonstrate how such transitions are linked to the catalytic sites of the eukaryotic proteasome, an essential protease of the ubiquitin pathway. The active sites of the cylindrical proteasomal core particle are located in a central chamber accessible through gated entry channels. By using atomic force microscopy, we found continual alternation between open and closed gate conformations. We analyzed the relative abundance of these conformers in wild-type and mutated yeast core particles upon exposure to substrates or inhibitors. Our data indicate that the dynamic gate can be opened by allosteric coupling to a tetrahedral transition state at any of the working active centers. The results point to the Nα-amine of the N-terminal active site threonyl residue as the major effector group responsible for triggering the essential conformational switch.

Original languageEnglish (US)
Pages (from-to)1137-1147
Number of pages11
JournalStructure
Volume17
Issue number8
DOIs
StatePublished - Aug 12 2009

Keywords

  • PROTEINS

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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