title: Substrate recognition by the Cdc20 and Cdh1 components of the anaphase-promoting complex.
abstract: The specificity of ubiquitin-mediated protein degradation with regards to the selection of substrates to be polyubiquitinated has only been determined rather recently. Substrate targeting by the N-end rule and HECT (homology to E6AP carboxyl terminus) domain ubiquitin ligases occurs through substrate-specific binding domains. In contrast, the SCF complex recruits substrates through a substrate adaptor protein, the F-box subunit. Despite evidence showing that Cdc20 and Cdh1 bind and activate the anaphase-promoting complex (APC) in a substrate-specific manner, there is no evidence that the activating protein and substrate interact directly; hence, no clear model exists for the mechanism of APC activation or recruitment of substrates. We show here that the activators Cdc20 and Cdh1 can associate with substrates via their N termini. In the absence of APC, Cdc20 and Cdh1 bind substrates reflecting Cdc20-APC and Cdh1-APC specificity. The N termini of Cdc20 and Cdh1 provide specificity functionally, as demonstrated by the generation of active chimeras that display the specificity corresponding to their N termini. Thus, Cdc20 and Cdh1 act as both substrate recognition and activating modules for APC.
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Pfleger
authors.forename: E
authors.initials: E
authors.lastname: Lee
authors.forename: M W
authors.initials: MW
authors.lastname: Kirschner
mesh_terms: D000595:Amino Acid Sequence; D064173:Anaphase-Promoting Complex-Cyclosome; D064199:Cdc20 Proteins; D064200:Cdh1 Proteins; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D008025:Ligases / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases
chemical_list: C577495:CDC20 protein, S cerevisiae; C577583:CDH1 protein, S cerevisiae; D064199:Cdc20 Proteins; D064200:Cdh1 Proteins; D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D044767:Ubiquitin-Protein Ligases; D008025:Ligases