title: The HEAT repeat protein Blm10 regulates the yeast proteasome by capping the core particle.
abstract: Proteasome activity is fine-tuned by associating the proteolytic core particle (CP) with stimulatory and inhibitory complexes. Although several mammalian regulatory complexes are known, knowledge of yeast proteasome regulators is limited to the 19-subunit regulatory particle (RP), which confers ubiquitin-dependence on proteasomes. Here we describe an alternative proteasome activator from Saccharomyces cerevisiae, Blm10. Synthetic interactions between blm10Delta and other mutations that impair proteasome function show that Blm10 functions together with proteasomes in vivo. This large, internally repetitive protein is found predominantly within hybrid Blm10-CP-RP complexes, representing a distinct pool of mature proteasomes. EM studies show that Blm10 has a highly elongated, curved structure. The near-circular profile of Blm10 adapts it to the end of the CP cylinder, where it is properly positioned to activate the CP by opening the axial channel into its proteolytic chamber.
authors.affiliation: Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA.
authors.forename: Marion
authors.initials: M
authors.lastname: Schmidt
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Haas
authors.forename: Bernat
authors.initials: B
authors.lastname: Crosas
authors.forename: Patricia G
authors.initials: PG
authors.lastname: Santamaria
authors.forename: Steven P
authors.initials: SP
authors.lastname: Gygi
authors.forename: Thomas
authors.initials: T
authors.lastname: Walz
authors.forename: Daniel
authors.initials: D
authors.lastname: Finley
mesh_terms: D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D017353:Gene Deletion; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000378:metabolism; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: C500597:Blm10 protein, S cerevisiae; D004268:DNA-Binding Proteins; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D021122:Protein Subunits; C119430:RPN4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D046988:Proteasome Endopeptidase Complex