title: The pore of activated 20S proteasomes has an ordered 7-fold symmetric conformation.
abstract: The 20S proteasome is a large multisubunit assembly that performs most of the intracellular non-lysosomal proteolysis of eukaryotes. Substrates access the proteasome active sites, which are sequestered in the interior of the barrel-shaped structure, through pores that are opened by binding of activator complexes. The crystal structure of yeast proteasome in complex with an 11S activator suggested that activation results from disordering of the proteasome gate residues. Here we report further analysis of this structure, which demonstrates that, in contrast to earlier models, the activated proteasome adopts an ordered 7-fold symmetric pore conformation that is stabilized by interactions formed by a cluster of highly conserved proteasome residues (Tyr8, Asp9, Pro17 and Tyr26). One non-canonical cluster, which appears to be mandated by the requirement that eukaryotic proteasomes also form an ordered closed conformation, explains all deviations from perfect conservation of these residues. We also demonstrate the importance of these conserved residues for proteolysis by an archaeal proteasome. Evolutionary considerations suggest that other activators might induce the same open proteasome conformation as seen with the 11S activator.
authors.affiliation: Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
authors.forename: Andreas
authors.initials: A
authors.lastname: Förster
authors.forename: Frank G
authors.initials: FG
authors.lastname: Whitby
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Hill
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D019843:Archaeal Proteins; D020134:Catalytic Domain; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010450:Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D006801:Humans; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D046988:Proteasome Endopeptidase Complex; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013822:Thermoplasma / Q000201:enzymology / Q000235:genetics
chemical_list: D019843:Archaeal Proteins; D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D011994:Recombinant Proteins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C093138:proteasome, Thermoplasma