Localization of the coactivator Cdh1 and the cullin subunit Apc2 in a cryo-electron microscopy model of vertebrate APC/C

Mol Cell. 2005 Dec 22;20(6):867-79. doi: 10.1016/j.molcel.2005.11.008.

Abstract

The anaphase-promoting complex/cyclosome (APC/C) is a ubiquitin ligase with essential functions in mitosis, meiosis, and G1 phase of the cell cycle. APC/C recognizes substrates via coactivator proteins such as Cdh1, and bound substrates are ubiquitinated by E2 enzymes that interact with a hetero-dimer of the RING subunit Apc11 and the cullin Apc2. We have obtained three-dimensional (3D) models of human and Xenopus APC/C by angular reconstitution and random conical tilt (RCT) analyses of negatively stained cryo-electron microscopy (cryo-EM) preparations, have determined the masses of these particles by scanning transmission electron microscopy (STEM), and have mapped the locations of Cdh1 and Apc2. These proteins are located on the same side of the asymmetric APC/C, implying that this is where substrates are ubiquitinated. We have further identified a large flexible domain in APC/C that adopts a different orientation upon Cdh1 binding. Cdh1 may thus activate APC/C both by recruiting substrates and by inducing conformational changes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anaphase-Promoting Complex-Cyclosome
  • Animals
  • Apc11 Subunit, Anaphase-Promoting Complex-Cyclosome
  • Cryoelectron Microscopy
  • Cullin Proteins / analysis*
  • Cullin Proteins / chemistry
  • Cullin Proteins / genetics
  • Cullin Proteins / metabolism
  • HeLa Cells
  • Humans
  • Models, Molecular
  • Molecular Weight
  • Protein Conformation*
  • Protein Subunits / chemistry*
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • Ubiquitin / metabolism
  • Ubiquitin-Protein Ligase Complexes / chemistry*
  • Ubiquitin-Protein Ligase Complexes / genetics
  • Ubiquitin-Protein Ligase Complexes / metabolism
  • Ubiquitin-Protein Ligases / analysis*
  • Ubiquitin-Protein Ligases / chemistry
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism
  • Xenopus laevis

Substances

  • Cullin Proteins
  • Protein Subunits
  • Ubiquitin
  • Ubiquitin-Protein Ligase Complexes
  • ANAPC11 protein, human
  • Anaphase-Promoting Complex-Cyclosome
  • Apc11 Subunit, Anaphase-Promoting Complex-Cyclosome
  • Ubiquitin-Protein Ligases