Properties of the beta subunit of the proteasome activator PA28 (11S REG)

S. Wilk, W. E. Chen, R. P. Magnusson

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15 Scopus citations


The proteasome activator PA28 (11S REG) is composed of two homologous subunits termed α and β. The properties of the recombinant β-subunit were explored and compared to the properties of the recombinant α-subunit. PA28β produced in an Escherichia coli expression system migrates on a calibrated gel filtration column as an apparent heptamer (M(r) = 250,000). Low concentrations of SDS (0.005%), dissociate the protein to a monomer (M(r) = 33,000). PA28β has a complex effect on proteasome activity. At concentrations which favor oligomerization (> 2 μM), PA28β is a strong proteasome activator although its affinity for the proteasome is about 10-fold less than recombinant PA28α. The catalytic properties of the PA28α and PA28β-activated proteasome are similar. At low concentrations, PA28β is a monomer and a potent allostetic proteasome inhibitor. These studies show that oligomerization of PA28β is required for proteasome activation and that PA28β monomers are potent proteasome inhibitors. (C) 2000 Academic Press.

Original languageEnglish
Pages (from-to)174-180
Number of pages7
JournalArchives of Biochemistry and Biophysics
Issue number1
StatePublished - 1 Dec 2000


  • 11S regulator
  • Multicatalytic proteinase complex
  • PA28
  • Proteasome
  • Proteasome activator
  • Proteasome inhibitor


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