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WD40 domain of Apc1 is critical for the coactivator-induced allosteric transition that stimulates APC/C catalytic activity

DOI: 10.1073/pnas.1607147113 DOI Help

Authors: Qiuhong Li (Medical Research Council Laboratory of Molecular Biology; Institute of Cancer Research) , Leifu Chang (MRC Laboratory of Molecular Biology) , Shintaro Aibara (MRC Laboratory of Molecular Biology) , Jing Yang (Medical Research Council Laboratory of Molecular Biology) , Ziguo Zhang (Medical Research Council Laboratory of Molecular Biology) , David Barford (Medical Research Council Laboratory of Molecular Biology)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Proceedings Of The National Academy Of Sciences

State: Published (Approved)
Published: September 2016
Diamond Proposal Number(s): 11235

Open Access Open Access

Abstract: The anaphase-promoting complex/cyclosome (APC/C) is a large multimeric cullin–RING E3 ubiquitin ligase that orchestrates cell-cycle progression by targeting cell-cycle regulatory proteins for destruction via the ubiquitin proteasome system. The APC/C assembly comprises two scaffolding subcomplexes: the platform and the TPR lobe that together coordinate the juxtaposition of the catalytic and substrate-recognition modules. The platform comprises APC/C subunits Apc1, Apc4, Apc5, and Apc15. Although the role of Apc1 as an APC/C scaffolding subunit has been characterized, its specific functions in contributing toward APC/C catalytic activity are not fully understood. Here, we report the crystal structure of the N-terminal domain of human Apc1 (Apc1N) determined at 2.2-Å resolution and provide an atomic-resolution description of the architecture of its WD40 (WD40 repeat) domain (Apc1WD40). To understand how Apc1WD40 contributes to APC/C activity, a mutant form of the APC/C with Apc1WD40 deleted was generated and evaluated biochemically and structurally. We found that the deletion of Apc1WD40 abolished the UbcH10-dependent ubiquitination of APC/C substrates without impairing the Ube2S-dependent ubiquitin chain elongation activity. A cryo-EM structure of an APC/C–Cdh1 complex with Apc1WD40 deleted showed that the mutant APC/C is locked into an inactive conformation in which the UbcH10-binding site of the catalytic module is inaccessible. Additionally, an EM density for Apc15 is not visible. Our data show that Apc1WD40 is required to mediate the coactivator-induced conformational change of the APC/C that is responsible for stimulating APC/C catalytic activity by promoting UbcH10 binding. In contrast, Ube2S activity toward APC/C substrates is not dependent on the initiation-competent conformation of the APC/C.

Journal Keywords: APC/C; ubiquitination; cell cycle; UbcH10; Ube2S

Subject Areas: Biology and Bio-materials

Instruments: I02-Macromolecular Crystallography

Added On: 19/09/2016 14:37


Discipline Tags:

Structural biology Life Sciences & Biotech

Technical Tags:

Diffraction Macromolecular Crystallography (MX)