Subcellular localization, stoichiometry, and protein levels of 26 S proteasome subunits in yeast

Steven Jon Russell, Katherine A. Steger, Stephen Albert Johnston

Research output: Contribution to journalArticle

133 Scopus citations

Abstract

The 26 S proteasome of eukaryotes is responsible for the degradation of proteins targeted for proteolysis by the ubiquitin system. Yeast has been an important model organism for understanding eukaryotic proteasome structure and function. Toward a quantitative characterization of the proteasome, we have determined the localization, cellular levels, and stoichiometry of proteasome subunits. The subcellular localization of two ATPase components of the regulatory complex of the proteasome, Sug2/Rpt4 and Sugl/Rpt6, and a subunit of the 20 S proteasome, Prel, were determined by immunofluorescence. In contrast to findings in multicellular organisms, these proteins are localized almost exclusively to the nucleus throughout the cell cycle. We have also determined the cellular abundance and stoichiometry of these proteasome subunits. Sugl/Rpt6, Sug2/Rpt4, and Prel are present in roughly equal stoichiometry with an abundance of 15,000-30,000 molecules/cell, corresponding to a concentration of 13-26 μM in the nucleus. Also, in contrast to mammalian cells, we find no evidence of a p27-containing 'modulator' of the proteasome in yeast. This information will be useful in comparing and contrasting the yeast and mammalian proteasomes and should contribute to a mechanistic understanding of how this complex functions.

Original languageEnglish (US)
Pages (from-to)21943-21952
Number of pages10
JournalJournal of Biological Chemistry
Volume274
Issue number31
DOIs
StatePublished - Jul 30 1999

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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