Structural insights into non-covalent ubiquitin activation of the cIAP1-UbcH5B~ubiquitin complex

Patel, A., Sibbet, G. J. and Huang, D. T. (2019) Structural insights into non-covalent ubiquitin activation of the cIAP1-UbcH5B~ubiquitin complex. Journal of Biological Chemistry, 294, pp. 1240-1249. (doi: 10.1074/jbc.RA118.006045) (PMID:30523153) (PMCID:PMC6349121)

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Abstract

Ubiquitin (Ub)-conjugating enzymes and Ub ligases control protein degradation and regulate many cellular processes in eukaryotes. Cellular inhibitor of apoptosis protein-1 (cIAP1) plays a central role in apoptosis and tumor necrosis factor signaling. It harbors a C-terminal RING domain that homodimerizes to recruit E2∼Ub (where ∼ denotes a thioester bond) complex to catalyze Ub transfer. Noncovalent Ub binding to the backside of the E2 Ub-conjugating enzyme UbcH5 has previously been shown to enhance RING domain activity, but the molecular basis for this enhancement is unclear. To investigate how dimeric cIAP1 RING activates E2∼Ub for Ub transfer and what role noncovalently bound Ub has in Ub transfer, here we determined the crystal structure of the cIAP1 RING dimer bound to both UbcH5B covalently linked to Ub (UbcH5B–Ub) and a noncovalent Ub to 1.7 Å resolution. The structure along with biochemical analyses revealed that the cIAP1 RING domain interacts with UbcH5B–Ub and thereby promotes the formation of a closed UbcH5B–Ub conformation that primes the thioester bond for Ub transfer. We observed that the noncovalent Ub binds to the backside of UbcH5B and abuts UbcH5B's α1β1-loop, which, in turn, stabilizes the closed UbcH5B–Ub conformation. Our results disclose the mechanism by which cIAP1 RING dimer activates UbcH5B∼Ub and indicate that noncovalent Ub binding further stabilizes the cIAP1-UbcH5B∼Ub complex in the active conformation to stimulate Ub transfer.

Item Type:Articles
Additional Information:This work was supported by Cancer Research UK Grant A23278 and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement 647849).
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Patel, Amrita and Huang, Professor Danny and Sibbet, Dr Gary
Authors: Patel, A., Sibbet, G. J., and Huang, D. T.
College/School:College of Medical Veterinary and Life Sciences
College of Medical Veterinary and Life Sciences > School of Cancer Sciences
Journal Name:Journal of Biological Chemistry
Publisher:American Society for Biochemistry and Molecular Biology, Inc.
ISSN:0021-9258
ISSN (Online):1083-351X
Published Online:06 December 2018
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Journal of Biological Chemistry 294: 1240-1249
Publisher Policy:Reproduced under a Creative Commons License

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