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PubMed · 12402045

The Doc1 subunit is a processivity factor for the anaphase-promoting complex.

Christopher W Carroll·David O Morgan
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Abstract

Ubiquitin-mediated proteolysis of securin and mitotic cyclins is essential for exit from mitosis. The final step in ubiquitination of these and other proteins is catalysed by the anaphase-promoting complex (APC), a multi-subunit ubiquitin-protein ligase (E3). Little is known about the molecular reaction resulting in APC-dependent substrate ubiquitination or the role of individual APC subunits in the reaction. Using a well-defined in vitro system, we show that highly purified APC from Saccharomyces cerevisiae ubiquitinates a model cyclin substrate in a processive manner. Analysis of mutant APC lacking the Doc1/Apc10 subunit (APC(doc1 Delta)) indicates that Doc1 is required for processivity. The specific molecular defect in APC(doc1 Delta) is identified by a large increase in apparent K(M) for the cyclin substrate relative to the wild-type enzyme. This suggests that Doc1 stimulates processivity by limiting substrate dissociation. Addition of recombinant Doc1 to APC(doc1 Delta) fully restores enzyme function. Doc1-related domains are found in mechanistically distinct ubiquitin-ligase enzymes and may generally stimulate ubiquitination by contributing to substrate-enzyme affinity.

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AnaphaseAnaphase-Promoting Complex-CyclosomeApc10 Subunit, Anaphase-Promoting Complex-CyclosomeCell CycleCell Cycle ProteinsDose-Response Relationship, DrugKineticsModels, BiologicalMutationProtein BindingProtein Structure, TertiaryRecombinant ProteinsSaccharomyces cerevisiaeSaccharomyces cerevisiae ProteinsSubstrate SpecificityTime FactorsUbiquitinUbiquitin-Protein Ligase ComplexesUbiquitin-Protein LigasesJournal ArticleResearch Support, U.S. Gov't, Non-P.H.S.Research Support, U.S. Gov't, P.H.S.

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Christopher W Carroll, David O Morgan. 2002. The Doc1 subunit is a processivity factor for the anaphase-promoting complex.. https://doi.org/10.1038/ncb871

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