The regulatory complex of Drosophila melanogaster 26S proteasomes: Subunit composition and localization of a deubiquitylating enzyme

Harald Hölzl, Barbara Kapelari, Josef Kellermann, Erika Seemüller, Máté Sümegi, Andor Udvardy, Ohad Medalia, Joseph Sperling, Shirley A. Müller, Andreas Engel, Wolfgang Baumeister

Research output: Contribution to journalArticlepeer-review

138 Scopus citations

Abstract

Drosophila melanogaster embryos are a source for homogeneous and stable 26S proteasomes suitable for structural studies. For biochemical characterization, purified 26S proteasomes were resolved by two-dimensional (2D) gel electrophoresis and subunits composing the regulatory complex (RC) were identified by amino acid sequencing and immunoblotting, before corresponding cDNAs were sequenced. 17 subunits from Drosophila RCs were found to have homologues in the yeast and human RCs. An additional subunit, p37A, not yet described in RCs of other organisms, is a member of the ubiquitin COOH-terminal hydrolase family (UCH). Analysis of EM images of 26S proteasomes-UCH-inhibitor complexes allowed for the first time to localize one of the RC's specific functions, deubiquitylating activity. The masses of 26S proteasomes with either one or two attached RCs were determined by scanning transmission EM (STEM), yielding a mass of 894 kD for a single RC. This value is in good agreement with the summed masses of the 18 identified RC subunits (932 kD), indicating that the number of subunits is complete.

Original languageEnglish
Pages (from-to)119-129
Number of pages11
JournalJournal of Cell Biology
Volume150
Issue number1
DOIs
StatePublished - 10 Jul 2000
Externally publishedYes

Keywords

  • ATP-dependent proteolysis
  • Electron microscopy
  • Protein degradation
  • Ubiquitin
  • Ubiquitin hydrolase

ASJC Scopus subject areas

  • Cell Biology

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