title: The structure of the mammalian 20S proteasome at 2.75 A resolution.
abstract: The 20S proteasome is the catalytic portion of the 26S proteasome. Constitutively expressed mammalian 20S proteasomes have three active subunits, beta 1, beta 2, and beta 5, which are replaced in the immunoproteasome by interferon-gamma-inducible subunits beta 1i, beta 2i, and beta 5i, respectively. Here we determined the crystal structure of the bovine 20S proteasome at 2.75 A resolution. The structures of alpha 2, beta 1, beta 5, beta 6, and beta 7 subunits of the bovine enzyme were different from the yeast enzyme but enabled the bovine proteasome to accommodate either the constitutive or the inducible subunits. A novel N-terminal nucleophile hydrolase activity was proposed for the beta 7 subunit. We also determined the site of the nuclear localization signals in the molecule. A model of the immunoproteasome was predicted from this constitutive structure.
authors.affiliation: Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Unno
authors.forename: Tsunehiro
authors.initials: T
authors.lastname: Mizushima
authors.forename: Yukio
authors.initials: Y
authors.lastname: Morimoto
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Tomisugi
authors.forename: Keiji
authors.initials: K
authors.lastname: Tanaka
authors.forename: Noritake
authors.initials: N
authors.lastname: Yasuoka
authors.forename: Tomitake
authors.initials: T
authors.lastname: Tsukihara
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D018360:Crystallography, X-Ray; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D008099:Liver / Q000201:enzymology; D008958:Models, Molecular; D015394:Molecular Structure; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000235:genetics; D046988:Proteasome Endopeptidase Complex; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D013379:Substrate Specificity
chemical_list: D009097:Multienzyme Complexes; D021122:Protein Subunits; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex