title: Molecular structure of the N-terminal domain of the APC/C subunit Cdc27 reveals a homo-dimeric tetratricopeptide repeat architecture.
abstract: The anaphase promoting complex/cyclosome (APC/C) is a large multi-subunit E3 ubiquitin ligase that targets specific cell cycle regulatory proteins for ubiquitin-dependent degradation, thereby controlling cell cycle events such as the metaphase to anaphase transition and the exit from mitosis. Biochemical and genetic studies are consistent with the notion that subunits of APC/C are organised into two distinct sub-complexes; a catalytic sub-complex including the cullin domain and RING finger subunits Apc2 and Apc11, respectively, and a tetratricopeptide repeat (TPR) sub-complex composed of the TPR subunits Cdc16, Cdc23 and Cdc27 (Apc3). Here, we describe the crystal structure of the N-terminal domain of Encephalitozoon cuniculi Cdc27 (Cdc27(Nterm)), revealing a homo-dimeric structure, composed predominantly of successive TPR motifs. Mutation of the Cdc27(Nterm) dimer interface destabilises the protein, disrupts dimerisation in solution, and abolishes the capacity of E. cuniculi Cdc27 to complement Saccharomyces cerevisiae Cdc27 in vivo. These results establish the existence of functional APC/C genes in E. cuniculi, the evolutionarily conserved dimeric properties of Cdc27, and provide a framework for understanding the architecture of full-length Cdc27.
authors.affiliation: Section of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, UK.
authors.forename: Ziguo
authors.initials: Z
authors.lastname: Zhang
authors.forename: S Mark
authors.initials: SM
authors.lastname: Roe
authors.forename: Marie
authors.initials: M
authors.lastname: Diogon
authors.forename: Eric
authors.initials: E
authors.lastname: Kong
authors.forename: Hicham
authors.initials: H
authors.lastname: El Alaoui
authors.forename: David
authors.initials: D
authors.lastname: Barford
mesh_terms: D064173:Anaphase-Promoting Complex-Cyclosome; D064190:Apc2 Subunit, Anaphase-Promoting Complex-Cyclosome; D064191:Apc3 Subunit, Anaphase-Promoting Complex-Cyclosome; D064196:Apc8 Subunit, Anaphase-Promoting Complex-Cyclosome; D018360:Crystallography, X-Ray; D009670:Encephalitozoon cuniculi / Q000201:enzymology*; D015394:Molecular Structure; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D020449:Repetitive Sequences, Amino Acid; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry; D043743:Ubiquitin-Protein Ligase Complexes / Q000737:chemistry*; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry*
chemical_list: D064191:Apc3 Subunit, Anaphase-Promoting Complex-Cyclosome; D064196:Apc8 Subunit, Anaphase-Promoting Complex-Cyclosome; C577441:CDC23 protein, S cerevisiae; C577355:CDC27 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D043743:Ubiquitin-Protein Ligase Complexes; C577346:APC2 protein, S cerevisiae; D064173:Anaphase-Promoting Complex-Cyclosome; D064190:Apc2 Subunit, Anaphase-Promoting Complex-Cyclosome; D044767:Ubiquitin-Protein Ligases