title: Disassembly of the self-assembled, double-ring structure of proteasome α7 homo-tetradecamer by α6.
abstract: The 20S core particle of the eukaryotic proteasome is composed of two α- and two β-rings, each of which is a hetero-heptamer composed of seven homologous but distinct subunits. Although formation of the eukaryotic proteasome is a highly ordered process assisted by assembly chaperones, α7, an α-ring component, has the unique property of self-assembling into a homo-tetradecamer. We used biophysical methods to characterize the oligomeric states of this proteasome subunit and its interaction with α6, which makes direct contacts with α7 in the proteasome α-ring. We determined a crystal structure of the α7 tetradecamer, which has a double-ring structure. Sedimentation velocity analytical ultracentrifugation and mass spectrometric analysis under non-denaturing conditions revealed that α7 exclusively exists as homo-tetradecamer in solution and that its double-ring structure is disassembled upon the addition of α6, resulting in a 1:7 hetero-octameric α6-α7 complex. Our findings suggest that proteasome formation involves the disassembly of non-native oligomers, which are assembly intermediates.
authors.affiliation: Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Ishii
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Noda
authors.affiliation: Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Aichi 467-8603, Japan.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Yagi
authors.affiliation: Faculty of Science, Kasetsart University, Bangkean, Bangkok 10900, Thailand.|Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan.
authors.forename: Ratsupa
authors.initials: R
authors.lastname: Thammaporn
authors.affiliation: Faculty of Science, Kasetsart University, Bangkean, Bangkok 10900, Thailand.|Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan.
authors.forename: Supaporn
authors.initials: S
authors.lastname: Seetaha
authors.affiliation: Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Aichi 467-8603, Japan.|JST, PRESTO, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Aichi 467-8603, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Satoh
authors.affiliation: Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan.|Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya, Aichi 467-8603, Japan.|Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Kato
authors.affiliation: Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan.|Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Uchiyama
mesh_terms: D018360:Crystallography, X-Ray; D006801:Humans; D013058:Mass Spectrometry; D008958:Models, Molecular; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D014461:Ultracentrifugation
chemical_list: C465641:PSMA6 protein, human; C488662:PSMA7 protein, human; D046988:Proteasome Endopeptidase Complex