title: Molecular architecture and mechanism of the anaphase-promoting complex.
abstract: The ubiquitination of cell cycle regulatory proteins by the anaphase-promoting complex/cyclosome (APC/C) controls sister chromatid segregation, cytokinesis and the establishment of the G1 phase of the cell cycle. The APC/C is an unusually large multimeric cullin-RING ligase. Its activity is strictly dependent on regulatory coactivator subunits that promote APC/C-substrate interactions and stimulate its catalytic reaction. Because the structures of many APC/C subunits and their organization within the assembly are unknown, the molecular basis for these processes is poorly understood. Here, from a cryo-electron microscopy reconstruction of a human APC/C-coactivator-substrate complex at 7.4 Å resolution, we have determined the complete secondary structural architecture of the complex. With this information we identified protein folds for structurally uncharacterized subunits, and the definitive location of all 20 APC/C subunits within the 1.2 MDa assembly. Comparison with apo APC/C shows that the coactivator promotes a profound allosteric transition involving displacement of the cullin-RING catalytic subunits relative to the degron-recognition module of coactivator and APC10. This transition is accompanied by increased flexibility of the cullin-RING subunits and enhanced affinity for UBCH10-ubiquitin, changes which may contribute to coactivator-mediated stimulation of APC/C E3 ligase activity.
authors.affiliation: Division of Structural Biology, Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB, UK.|MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK.
authors.forename: Lei-Fu
authors.initials: LF
authors.lastname: Chang
authors.affiliation: Division of Structural Biology, Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB, UK.|MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK.
authors.forename: Ziguo
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Division of Structural Biology, Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB, UK.|MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK.
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.affiliation: MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK.
authors.forename: Stephen H
authors.initials: SH
authors.lastname: McLaughlin
authors.affiliation: Division of Structural Biology, Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB, UK.|MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK.
authors.forename: David
authors.initials: D
authors.lastname: Barford
mesh_terms: D000494:Allosteric Regulation; D064173:Anaphase-Promoting Complex-Cyclosome / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure*; D064197:Apc10 Subunit, Anaphase-Promoting Complex-Cyclosome / Q000737:chemistry / Q000378:metabolism; D020134:Catalytic Domain; D064200:Cdh1 Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D020285:Cryoelectron Microscopy; D006801:Humans; D008958:Models, Molecular; D018583:Pliability; D017510:Protein Folding; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism; D054875:Ubiquitination
chemical_list: C577455:ANAPC10 protein, human; D064197:Apc10 Subunit, Anaphase-Promoting Complex-Cyclosome; D064200:Cdh1 Proteins; D021122:Protein Subunits; D025801:Ubiquitin; C105156:UBE2C protein, human; D044763:Ubiquitin-Conjugating Enzymes; D064173:Anaphase-Promoting Complex-Cyclosome