title: The proteasome inhibitor PI31 competes with PA28 for binding to 20S proteasomes.
abstract: PI31 is a previously described inhibitor of 20S proteasomes. Using recombinant PI31 we have analyzed its effect on proteasomal hydrolyzing activity of short fluorogenic substrates and of a synthetic 40-mer polypeptide. In addition, we investigated its influence on the activation of 20S proteasome by the proteasome activator PA28. PI31 inhibits polypeptide degradation already at concentrations which only partially inhibit fluorogenic substrate turnover and immunosubunits do not influence the PI31 binding affinity. Furthermore our data demonstrate that PI31 is a potent competitor of PA28-mediated activation.
authors.affiliation: Institute of Biochemistry/Charité, Monbijou Strasse 2, D-10117, Berlin, Germany.
authors.forename: D M
authors.initials: DM
authors.lastname: Zaiss
authors.forename: S
authors.initials: S
authors.lastname: Standera
authors.forename: H
authors.initials: H
authors.lastname: Holzhütter
authors.forename: P
authors.initials: P
authors.lastname: Kloetzel
authors.forename: A J
authors.initials: AJ
authors.lastname: Sijts
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001324:Autoantigens; D001667:Binding, Competitive; D002460:Cell Line / Q000187:drug effects / Q000378:metabolism; D003001:Cloning, Molecular; D003546:Cysteine Endopeptidases / Q000187:drug effects / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology; D004789:Enzyme Activation; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000187:drug effects / Q000378:metabolism*; D009124:Muscle Proteins; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D001324:Autoantigens; D015853:Cysteine Proteinase Inhibitors; C099558:Ki antigen; D009097:Multienzyme Complexes; D009124:Muscle Proteins; C085047:PSME1 protein, human; C121623:PSMF1 protein, human; D011506:Proteins; D011993:Recombinant Fusion Proteins; D007371:Interferon-gamma; D005982:Glutathione Transferase; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex