title: Increased degradation of oxidized proteins in yeast defective in 26 S proteasome assembly.
abstract: An Rpn9-disrupted yeast strain, Delta rpn9, whose growth is temperature sensitive with defective assembly of the 26 S proteasome complex, was studied. This mutant yeast was more resistant to hydrogen peroxide treatment and able to degrade carbonylated proteins more efficiently than wild type. Nondenaturing gel electrophoresis followed by activity staining revealed that Delta rpn9 yeast cells had a higher activity of 20 S proteasome than wild type and that in both Delta rpn9 and wild-type cells treated with hydrogen peroxide, 20 S proteasome activity was increased with a concomitant decrease in 26 S proteasome activity. Protein multiubiquitination was not observed in the hydrogen peroxide-treated cells. Taken together, these results suggest that the 20 S proteasome degrades oxidized proteins without ubiquitination of target proteins.
authors.affiliation: Department of Biochemistry, Wakayama Medical University, 811-1 Kimiidera, Wakayama 641-0012, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Inai
authors.forename: Morimitsu
authors.initials: M
authors.lastname: Nishikimi
mesh_terms: D000447:Aldehydes / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007659:Ketones / Q000378:metabolism; D046911:Macromolecular Substances; D009097:Multienzyme Complexes / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology; D010447:Peptide Hydrolases / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011506:Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D000447:Aldehydes; D007659:Ketones; D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D016877:Oxidants; D011506:Proteins; D025801:Ubiquitin; D006861:Hydrogen Peroxide; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease