TPR subunits of the anaphase-promoting complex mediate binding to the activator protein CDH1.
BACKGROUND: Chromosome segregation and mitotic exit depend on activation of the anaphase-promoting complex (APC) by the substrate adaptor proteins CDC20 and CDH1. The APC is a ubiquitin ligase composed of at least 11 subunits. The interaction of APC2 and APC11 with E2 enzymes is sufficient for ubiquitination reactions, but the functions of most other subunits are unknown. RESULTS: We have biochemically characterized subcomplexes of the human APC. One subcomplex, containing APC2/11, APC1, APC4, and APC5, can assemble multiubiquitin chains but is unable to bind CDH1 and to ubiquitinate substrates. The other subcomplex contains all known APC subunits except APC2/11. This subcomplex can recruit CDH1 but fails to support any ubiquitination reaction. In vitro, the C termini of CDC20 and CDH1 bind to the closely related TPR subunits APC3 and APC7. Homology modeling predicts that these proteins are similar in structure to the peroxisomal import receptor PEX5, which binds cargo proteins via their C termini. APC activation by CDH1 depends on a conserved C-terminal motif that is also found in CDC20 and APC10. CONCLUSIONS: APC1, APC4, and APC5 may connect APC2/11 with TPR subunits. TPR domains in APC3 and APC7 recruit CDH1 to the APC and may thereby bring substrates into close proximity of APC2/11 and E2 enzymes. In analogy to PEX5, the different TPR subunits of the APC might function as receptors that interact with the C termini of regulatory proteins such as CDH1, CDC20, and APC10.
Pubmed ID: 12956947 RIS Download
Amino Acid Sequence | Anaphase-Promoting Complex-Cyclosome | Apc1 Subunit, Anaphase-Promoting Complex-Cyclosome | Apc11 Subunit, Anaphase-Promoting Complex-Cyclosome | Apc4 Subunit, Anaphase-Promoting Complex-Cyclosome | Apc5 Subunit, Anaphase-Promoting Complex-Cyclosome | Apc7 Subunit, Anaphase-Promoting Complex-Cyclosome | Blotting, Western | Cdc20 Proteins | Cell Cycle | Cell Cycle Proteins | Electrophoresis, Polyacrylamide Gel | Humans | In Vitro Techniques | Molecular Sequence Data | Protein Conformation | Sequence Homology | Silver Staining | Ubiquitin-Activating Enzymes | Ubiquitin-Protein Ligase Complexes | Ubiquitin-Protein Ligases