Atomic-Resolution Structures of the APC/C Subunits Apc4 and the Apc5 N-Terminal Domain.
Many essential biological processes are mediated by complex molecular machines comprising multiple subunits. Knowledge on the architecture of individual subunits and their positions within the overall multimeric complex is key to understanding the molecular mechanisms of macromolecular assemblies. The anaphase-promoting complex/cyclosome (APC/C) is a large multisubunit complex that regulates cell cycle progression by ubiquitinating cell cycle proteins for proteolysis by the proteasome. The holo-complex is composed of 15 different proteins that assemble to generate a complex of 20 subunits. Here, we describe the crystal structures of Apc4 and the N-terminal domain of Apc5 (Apc5(N)). Apc4 comprises a WD40 domain split by a long α-helical domain, whereas Apc5(N) has an α-helical fold. In a separate study, we had fitted these atomic models to a 3.6-Å-resolution cryo-electron microscopy map of the APC/C. We describe how, in the context of the APC/C, regions of Apc4 disordered in the crystal assume order through contacts to Apc5, whereas Apc5(N) shows small conformational changes relative to its crystal structure. We discuss the complementary approaches of high-resolution electron microscopy and protein crystallography to the structure determination of subunits of multimeric complexes.
Division of Structural Biology, Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, United Kingdom.
Nora B
NB
Cronin
Division of Structural Biology, Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, United Kingdom; MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom.
Jing
J
Yang
Division of Structural Biology, Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, United Kingdom; MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom.
Ziguo
Z
Zhang
Division of Structural Biology, Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, United Kingdom; Division of Biochemical Sciences, Council of Scientific and Industrial Research National Chemical Laboratory, Pune 411008, India.
Kiran
K
Kulkarni
Division of Structural Biology, Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, United Kingdom; MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom.
Leifu
L
Chang
Cancer Institute, University College London, Paul O'Gorman Building, 72 Huntley Street, London WC1E 6BT, United Kingdom.
Hiroyuki
H
Yamano
Division of Structural Biology, Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, United Kingdom; MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, United Kingdom. Electronic address: dbarford@mrc-lmb.cam.ac.uk.
David
D
Barford
D000818:Animals; D064192:Apc4 Subunit, Anaphase-Promoting Complex-Cyclosome / Q000648:ultrastructure*; D064193:Apc5 Subunit, Anaphase-Promoting Complex-Cyclosome / Q000648:ultrastructure*; D002453:Cell Cycle / Q000502:physiology; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000378:metabolism*; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces; D014982:Xenopus laevis
D064192:Apc4 Subunit, Anaphase-Promoting Complex-Cyclosome; D064193:Apc5 Subunit, Anaphase-Promoting Complex-Cyclosome; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins
anaphase-promoting complex; cell cycle; multisubunit structure; protein crystallography; ubiquitin