title: Reconfiguration of the proteasome during chaperone-mediated assembly.
abstract: The proteasomal ATPase ring, comprising Rpt1-Rpt6, associates with the heptameric α-ring of the proteasome core particle (CP) in the mature proteasome, with the Rpt carboxy-terminal tails inserting into pockets of the α-ring. Rpt ring assembly is mediated by four chaperones, each binding a distinct Rpt subunit. Here we report that the base subassembly of the Saccharomyces cerevisiae proteasome, which includes the Rpt ring, forms a high-affinity complex with the CP. This complex is subject to active dissociation by the chaperones Hsm3, Nas6 and Rpn14. Chaperone-mediated dissociation was abrogated by a non-hydrolysable ATP analogue, indicating that chaperone action is coupled to nucleotide hydrolysis by the Rpt ring. Unexpectedly, synthetic Rpt tail peptides bound α-pockets with poor specificity, except for Rpt6, which uniquely bound the α2/α3-pocket. Although the Rpt6 tail is not visualized within an α-pocket in mature proteasomes, it inserts into the α2/α3-pocket in the base-CP complex and is important for complex formation. Thus, the Rpt-CP interface is reconfigured when the lid complex joins the nascent proteasome to form the mature holoenzyme.
authors: Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA.
authors: Soyeon
authors: S
authors: Park
authors: Xueming
authors: X
authors: Li
authors: Ho Min
authors: HM
authors: Kim
authors: Chingakham Ranjit
authors: CR
authors: Singh
authors: Geng
authors: G
authors: Tian
authors: Martin A
authors: MA
authors: Hoyt
authors: Scott
authors: S
authors: Lovell
authors: Kevin P
authors: KP
authors: Battaile
authors: Michal
authors: M
authors: Zolkiewski
authors: Philip
authors: P
authors: Coffino
authors: Jeroen
authors: J
authors: Roelofs
authors: Yifan
authors: Y
authors: Cheng
authors: Daniel
authors: D
authors: Finley
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism; D020285:Cryoelectron Microscopy; D020035:Holoenzymes / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; C112193:HSM3 protein, S cerevisiae; D020035:Holoenzymes; D018832:Molecular Chaperones; C114551:NAS6 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D000255:Adenosine Triphosphate; D046988:Proteasome Endopeptidase Complex; C542569:Rpn14 protein, S cerevisiae; D000251:Adenosine Triphosphatases; C069670:RPT6 protein, S cerevisiae
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