title: Heterohexameric ring arrangement of the eukaryotic proteasomal ATPases: implications for proteasome structure and assembly.
abstract: The proteasome has a paramount role in eukaryotic cell regulation. It consists of a proteolytic core particle (CP) bound to one or two regulatory particles (RPs). Each RP is believed to include six different AAA+ ATPases in a heterohexameric ring that binds the CP while unfolding and translocating substrates into the core. No atomic-resolution RP structures are available. Guided by crystal structures of related homohexameric prokaryotic ATPases, we use disulfide engineering to show that the eukaryotic ATPases form a ring with the arrangement Rpt1-Rpt2-Rpt6-Rpt3-Rpt4-Rpt5 in fully assembled proteasomes. The arrangement is consistent with known assembly intermediates. This quaternary organization clarifies the functional overlap of specific RP assembly chaperones and led us to identify a potential RP assembly intermediate that includes four ATPases (Rpt6-Rpt3-Rpt4-Rpt5) and their cognate chaperones (Rpn14, Nas6, and Nas2). Finally, the ATPase ring structure casts light on alternative RP structural models and the mechanism of RP action.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06520-8114, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Tomko
authors.forename: Minoru
authors.initials: M
authors.lastname: Funakoshi
authors.forename: Kyle
authors.initials: K
authors.lastname: Schneider
authors.forename: Jimin
authors.initials: J
authors.lastname: Wang
authors.forename: Mark
authors.initials: M
authors.lastname: Hochstrasser
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry; D004220:Disulfides / Q000737:chemistry; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry; D046912:Multiprotein Complexes; D009154:Mutation; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015202:Protein Engineering; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D013329:Structure-Activity Relationship; D015003:Yeasts / Q000201:enzymology* / Q000235:genetics
chemical_list: D004220:Disulfides; D005656:Fungal Proteins; D018832:Molecular Chaperones; D046912:Multiprotein Complexes; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D000251:Adenosine Triphosphatases; D003545:Cysteine
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