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

Proc Natl Acad Sci U S A. 2016 Sep 20;113(38):10547-52. doi: 10.1073/pnas.1607147113. Epub 2016 Sep 6.


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 (Apc1(WD40)). To understand how Apc1(WD40) contributes to APC/C activity, a mutant form of the APC/C with Apc1(WD40) deleted was generated and evaluated biochemically and structurally. We found that the deletion of Apc1(WD40) 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 Apc1(WD40) 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 Apc1(WD40) 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.

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

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Allosteric Regulation / genetics
  • Anaphase-Promoting Complex-Cyclosome / chemistry*
  • Anaphase-Promoting Complex-Cyclosome / genetics
  • Antigens, CD
  • Apc1 Subunit, Anaphase-Promoting Complex-Cyclosome / chemistry*
  • Apc1 Subunit, Anaphase-Promoting Complex-Cyclosome / genetics
  • Binding Sites
  • Cadherins / chemistry*
  • Cadherins / genetics
  • Cell Cycle Proteins / chemistry*
  • Cell Cycle Proteins / genetics
  • Crystallography, X-Ray
  • Humans
  • Mutant Proteins / chemistry*
  • Mutant Proteins / genetics
  • Protein Binding
  • Protein Conformation
  • Protein Domains
  • Ubiquitin / chemistry
  • Ubiquitin / genetics
  • Ubiquitin-Conjugating Enzymes / chemistry
  • Ubiquitin-Conjugating Enzymes / genetics
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitination / genetics
  • WD40 Repeats / genetics


  • ANAPC1 protein, human
  • ANAPC15 protein, human
  • Antigens, CD
  • Apc1 Subunit, Anaphase-Promoting Complex-Cyclosome
  • CDH1 protein, human
  • Cadherins
  • Cell Cycle Proteins
  • Mutant Proteins
  • Ubiquitin
  • UBE2C protein, human
  • Ube2S protein, human
  • Ubiquitin-Conjugating Enzymes
  • Anaphase-Promoting Complex-Cyclosome
  • CULL-RING ligase, human
  • Ubiquitin-Protein Ligases

Associated data

  • PDB/5LGG