Structures of Rpn1 T1:Rad23 and hRpn13:hPLIC2 Reveal Distinct Binding Mechanisms between Substrate Receptors and Shuttle Factors of the Proteasome

Xiang Chen, Leah Randles, Ke Shi, Sergey G. Tarasov, Hideki Aihara, Kylie J. Walters

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

Three receptors (Rpn1/S2/PSMD2, Rpn10/S5a, Rpn13/Adrm1) in the proteasome bind substrates by interacting with conjugated ubiquitin chains and/or shuttle factors (Rad23/HR23, Dsk2/PLIC/ubiquilin, Ddi1) that carry ubiquitinated substrates to proteasomes. We solved the structure of two such receptors with their preferred shuttle factor, namely hRpn13Pru:hPLIC2UBL and scRpn1 T1:scRad23UBL. We find that ubiquitin folds in Rad23 and Dsk2 are fine-tuned by residue substitutions to achieve high affinity for Rpn1 and Rpn13, respectively. A single substitution in hPLIC2 yields enhanced interactions with the Rpn13 ubiquitin contact surface and sterically blocks hRpn13 binding to its preferred ubiquitin chain type, K48-linked chains. Rpn1 T1 binds two ubiquitins in tandem and we find that Rad23 binds exclusively to the higher-affinity Helix28/Helix30 site. Rad23 contacts at Helix28/Helix30 are optimized compared to ubiquitin by multiple conservative amino acid substitutions. Thus, shuttle factors deliver substrates to proteasomes through fine-tuned ubiquitin-like surfaces.

Original languageEnglish (US)
Pages (from-to)1257-1270
Number of pages14
JournalStructure
Volume24
Issue number8
DOIs
StatePublished - Aug 2 2016

Bibliographical note

Funding Information:
This research was funded by the Intramural Research Program of the NIH, National Cancer Institute, Center for Cancer Research to K.J.W. and a grant from the NIH to H.A. ( GM095558 ). X-ray data were collected at the Advanced Photon Source (APS) NE-CAT beamlines, which are supported by the NIGMS ( P41 GM103403 ). APS is a US Department of Energy Office of Science User Facility operated by Argonne National Laboratory under Contract DE-AC02-06CH11357 .

Publisher Copyright:
© 2016

Keywords

  • Dsk2
  • Rad23
  • Rpn1
  • Rpn13
  • proteasome
  • ubiquitin

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