4jpo
From Proteopedia
5A resolution structure of Proteasome Assembly Chaperone Hsm3 in complex with a C-terminal fragment of Rpt1
Structural highlights
Function[HSM3_YEAST] Involved in DNA mismatch repair in slow-growing cells. Acts as a chaperone during the assembly of the 26S proteasome, specifically of the base subcomplex of the 19S regulatory complex (RC).[1] [2] [3] [4] [5] [6] [7] [PRS7_YEAST] The 26S protease is involved in the ATP-dependent degradation of ubiquitinated proteins. The regulatory (or ATPase) complex confers ATP dependency and substrate specificity to the 26S complex (By similarity). Publication Abstract from PubMedThe proteasomal ATPase ring, comprising Rpt1-Rpt6, associates with the heptameric alpha-ring of the proteasome core particle (CP) in the mature proteasome, with the Rpt carboxy-terminal tails inserting into pockets of the alpha-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 alpha-pockets with poor specificity, except for Rpt6, which uniquely bound the alpha2/alpha3-pocket. Although the Rpt6 tail is not visualized within an alpha-pocket in mature proteasomes, it inserts into the alpha2/alpha3-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. Reconfiguration of the proteasome during chaperone-mediated assembly.,Park S, Li X, Kim HM, Singh CR, Tian G, Hoyt MA, Lovell S, Battaile KP, Zolkiewski M, Coffino P, Roelofs J, Cheng Y, Finley D Nature. 2013 May 23;497(7450):512-6. doi: 10.1038/nature12123. Epub 2013 May 5. PMID:23644457[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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