The ubiquitylation of cell-cycle regulatory proteins by the large multimeric anaphase-promoting complex (APC/C) controls sister chromatid segregation and the exit from mitosis. Selection of APC/C targets is achieved through recognition of destruction motifs, predominantly the destruction (D)-box and KEN (Lys-Glu-Asn)-box. Although this process is known to involve a co-activator protein (either Cdc20 or Cdh1) together with core APC/C subunits, the structural basis for substrate recognition and ubiquitylation is not understood. Here we investigate budding yeast APC/C using single-particle electron microscopy and determine a cryo-electron microscopy map of APC/C in complex with the Cdh1 co-activator protein (APC/C(Cdh1)) bound to a D-box peptide at ∼10 Å resolution. We find that a combined catalytic and substrate-recognition module is located within the central cavity of the APC/C assembled from Cdh1, Apc10--a core APC/C subunit previously implicated in substrate recognition--and the cullin domain of Apc2. Cdh1 and Apc10, identified from difference maps, create a co-receptor for the D-box following repositioning of Cdh1 towards Apc10. Using NMR spectroscopy we demonstrate specific D-box-Apc10 interactions, consistent with a role for Apc10 in directly contributing towards D-box recognition by the APC/C(Cdh1) complex. Our results rationalize the contribution of both co-activator and core APC/C subunits to D-box recognition and provide a structural framework for understanding mechanisms of substrate recognition and catalysis by the APC/C.
Pubmed ID: 21107322 RIS Download
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A user-sponsored molecular visualization software system on an open-source foundation. The software has the capabilities to view, render, animate, export, present and develop three dimensional molecular structures.
View all literature mentionsAn image analysis software that can process spectra and other multi-dimensional data-sets. The software package is aimed at processing large data sets from (cryo-) electron microscopy, especially in the field of single particle analyses. This software can be used with light and raster-tunneling microscopes, computer tomographs, FT-IR spectrometers and other signal collecting devices. This resource provides three-dimensional data processing and angular reconstitution modules that allow the three-dimensional reconstruction with point-group symmetry from the two dimensional electron microscopy projections. These models aid in the analysis of the macromolecules.
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