PSI Structural Biology Knowledgebase

PSI | Structural Biology Knowledgebase
Header Icons
E-Collection

Related Articles
Community-Nominated Targets
July 2015
Drug Discovery: Solving the Structure of an Anti-hypertension Drug Target
July 2015
Retrospective: 7,000 Structures Closer to Understanding Biology
July 2015
Design and Evolution: Unveiling Translocator Proteins
June 2015
Signaling with DivL
May 2015
Signaling: A Platform for Opposing Functions
May 2015
Signaling: Securing Lipid-Protein Partnership
May 2015
Dynamic DnaK
March 2015
Iron-Sulfur Cluster Biosynthesis
December 2014
Mitochondrion: Flipping for UCP2
December 2014
Mitochondrion: Setting a New TRAP1
December 2014
Power in Numbers
August 2014
Quorum Sensing: A Groovy New Component
August 2014
Quorum Sensing: E. coli Gets Involved
August 2014
iTRAQing the Ubiquitinome
July 2014
Microbiome: The Dynamics of Infection
September 2013
Protein-Nucleic Acid Interaction: A Modified SAM to Modify tRNA
July 2013
Protein-Nucleic Acid Interaction: Versatile Glutamate
July 2013
PDZ Domains
April 2013
Alpha-Catenin Connections
March 2013
Cell-Cell Interaction: A FERM Connection
March 2013
Cell-Cell Interaction: Magic Structure from Microcrystals
March 2013
Cell-Cell Interaction: Modulating Self Recognition Affinity
March 2013
Bacterial Hemophores
January 2013
Archaeal Lipids
December 2012
Membrane Proteome: Capturing Multiple Conformations
December 2012
Lethal Tendencies
October 2012
Symmetry from Asymmetry
October 2012
A signal sensing switch
September 2012
Regulatory insights
September 2012
AlkB Homologs
August 2012
Budding ensemble
August 2012
Targeting Enzyme Function with Structural Genomics
July 2012
The machines behind the spindle assembly checkpoint
June 2012
Chaperone interactions
April 2012
Pilus Assembly Protein TadZ
April 2012
Revealing the Nuclear Pore Complex
March 2012
Topping off the proteasome
March 2012
Twist to open
March 2012
Disordered Proteins
February 2012
Analyzing an allergen
January 2012
Making Lipopolysaccharide
January 2012
Pulling on loose ends
January 2012
Terminal activation
December 2011
The Perils of Protein Secretion
November 2011
Bacterial Armor
October 2011
TLR4 regulation: heads or tails?
October 2011
Ribose production on demand
September 2011
Moving some metal
August 2011
Looking for lipids
July 2011
Ribofuranosyl Binding Protein
June 2011
A molecular switch for neuronal growth
May 2011
Cell wall recycler
May 2011
Added benefits
April 2011
NMR challenges current protein hydration dogma
March 2011
Nitrile Reductase QueF
March 2011
Tip formin
March 2011
Inhibiting factor
February 2011
PASK staying active
February 2011
Tryptophanyl-tRNA Synthetase
February 2011
Regulating nitrogen assimilation
January 2011
Subtle shifts
January 2011
Nitrobindin
December 2010
Function following form
October 2010
tRNA Isopentenyltransferase MiaA
August 2010
Importance of extension for integrin
June 2010
Phytochrome
April 2010
Alg13 Subunit of N-Acetylglucosamine Transferase
February 2010
Hemolysin BL
January 2010
Secretagogin
December 2009
Two-component signaling
December 2009
Network coverage
November 2009
Pseudouridine Synthase TruA
November 2009
Unusual cell division
October 2009
Toxin-antitoxin VapBC-5
September 2009
Salicylic Acid Binding Protein 2
August 2009
Proofreading RNA
July 2009
Ykul structure solves bacterial signaling puzzle
July 2009
Hda and DNA Replication
June 2009
Controlling p53
May 2009
Mitotic checkpoint control
May 2009
Ribonuclease and Ribonuclease Inhibitor
April 2009
The elusive helicase
April 2009
Aquaglyceroporin
March 2009
High-energy storage system
February 2009
A new class of bacterial E3 ubiquitination enzymes
January 2009
Poly(A) RNA recognition
January 2009
Activating BAX
December 2008
Scavenger Decapping Enzyme DcpS
November 2008
Bacteriophage Lambda cII Protein
October 2008
New metal-binding domain
October 2008
Blocking AmtB
September 2008
T-Rex
September 2008
Aspartate Dehydrogenase
August 2008
RNase T
July 2008
Chronophin
May 2008

Research Themes Cell biology

Mitotic checkpoint control

PSI-SGKB [doi:10.1038/fa_psisgkb.2009.18]
Featured Article - May 2009
Short description: The molecular basis of inhibition of the anaphase-promoting complex/cyclosome revealed.Science 323, 1477-1481 (2009)

The APC/C structure. (Top) Apo-APC/C with proteins labeled according to the antibody labeling experiments. (Bottom) APC/C in complex with the mitotic checkpoint complex (MCC, red).

Chromosome segregation is carefully regulated to reduce defects arising from abnormal numbers of chromosomes. Cell division is halted by the spindle checkpoint until all chromosomes are connected to the mitotic or meiotic spindle, and only once they are correctly attached does the next step of the cell cycle, anaphase, begin. The anaphase-promoting complex/cyclosome (APC/C), an E3 ubiquitin-protein ligase, and its coactivator Cdc20 are crucial for cell-cycle progression, and now a new study in Science by Herzog et al. 1 reveals how they are inhibited by spindle checkpoint proteins.

APC/C was purified in two different states. Checkpoint-inhibited APC/C was isolated from HeLa cells trapped in an early phase of mitosis, prometaphase, by addition of the chemical taxol. An inactive form of APC/C was isolated from cells in which the checkpoint had been inactivated by the kinase inhibitor Hesperadin. Four times the amount of checkpoint proteins were associated with APC/C in cells in which the checkpoint was active than in Hesperadin-treated cells.

Further examination of the active checkpoint revealed two forms of active APC/C. One contains the mitotic checkpoint proteins BubR1, Bub3, Cdc20 and Mad2 (together known as APC/CMCC); the other lacks these additional proteins (and is known as apo-ACP/C).

The structures of APC/CMCC and apo-APC/C were examined by electron microscopy, along with that of apo-APC/C with Cdc20 bound (APC/CCdc20). The team used angular reconstitution techniques to build three-dimensional models and showed that apo-APC/C consists of two domains: the 'platform' and the 'arc lamp'. These domains exist in three different relative conformations, which probably reflects flexibility in the complex.

By analyzing APC/CMCC, the authors established that a large additional density at the 'front' of the platform domain corresponds to the proteins of the mitotic checkpoint complex and that addition of this complex locks APC/C in a closed conformation. A further three-dimensional model of apo-APC with Cdc20 bound showed a 50 kDa mass on the front of APC/C that partly overlaps the site where MCC binds to the APC/C.

These studies show that upon activation, the mitotic checkpoint proteins BubR1, Bub3 and Mad2 associate with APC/CCdc20. In biochemical experiments the authors observed that the binding of checkpoint proteins to APC/C coincides with loss of substrate binding. These findings indicate that the checkpoint proteins inhibit APC/C by preventing the recruitment of substrates. Because previous work has revealed that Cdc20 functions as a substrate adaptor, the authors speculate that binding of checkpoint proteins to Cdc20 may prevent substrates binding to the APC/CCdc20 active site.

Maria Hodges

References

  1. F. Herzog et al. Structure of the anaphase-promoting complex/cyclosome interacting with a mitotic checkpoint complex.
    Science 323, 1477-1481 (2009).

Structural Biology Knowledgebase ISSN: 1758-1338
Funded by a grant from the National Institute of General Medical Sciences of the National Institutes of Health