The proteasome subunit, C2, contains an important site for binding of the PA28 (11S) activator

Mary A. Kania, George N. Demartino, Wolfgang Baumeister, Alfred L. Goldberg

Research output: Contribution to journalArticlepeer-review

42 Scopus citations


The PA28, or 11S regulatory complex, stimulates the peptidase activities of the 20S proteasome. Monoclonal antibodies were screened for their ability to inhibit the activation by PA28 of proteasomes from rabbit reticulocytes. We identified one antibody that inhibited proteasome activation by PA28 and dissociated formed proteasome-PA28 complexes. A fourfold molar excess of antibody to proteasome markedly reduced the PA28 activation of three peptidase activities. Examination of proteasome-antibody mixtures by electron microscopy revealed that the antibody formed chains of proteasomes, and digital image analysis of individual proteasomes demonstrated that the antibody binds to the outer α rings. This antibody recognizes proteasome subunit C2, which we conclude contains an important contact site for the PA28 activator. However, the antibody did not block proteasome activation by PA700, or 19S regulator, which also associates with the α rings. Thus, these two regulators appear to bind to the proteasome at different sites.

Original languageEnglish (US)
Pages (from-to)510-516
Number of pages7
JournalEuropean Journal of Biochemistry
Issue number2
StatePublished - 1996


  • PA28
  • antibody
  • proteasome
  • proteasome activation

ASJC Scopus subject areas

  • Biochemistry


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