title: Specificity of the anaphase-promoting complex: a single-molecule study.
abstract: Biological processes require specific enzymatic reactions, paradoxically involving short recognition sequences. As an example, cell-cycle timing depends on a sequence of ubiquitylation events mediated by the anaphase-promoting complex (APC) based on short redundant motifs. To understand the origin of specificity, we designed single-molecule fluorescence assays that capture transient ubiquitylation reactions. We find that the APC-mediated ubiquitylation involves a highly processive initial reaction on the substrate, followed by multiple encounters and reactions at a slower rate. The initial ubiquitylation greatly enhances the substrate's binding affinity in subsequent reactions, by both increasing the on-rate and decreasing the off-rate. We postulate that these cycles of positive feedback enable high specificity for substrates with short recognition motifs in a complex cellular environment.
authors: Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.
authors: Ying
authors: Y
authors: Lu
authors: Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.
authors: Weiping
authors: W
authors: Wang
authors: Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA. marc@hms.harvard.edu.
authors: Marc W
authors: MW
authors: Kirschner
mesh_terms: D064173:Anaphase-Promoting Complex-Cyclosome / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D002453:Cell Cycle; D019925:Cyclin A / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D025461:Feedback, Physiological; D005453:Fluorescence; D005456:Fluorescent Dyes; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D055532:SMN Complex Proteins / Q000378:metabolism; D013379:Substrate Specificity; D025801:Ubiquitin / Q000378:metabolism; D054875:Ubiquitination
chemical_list: D019925:Cyclin A; D019926:Cyclin B; D005456:Fluorescent Dyes; D055532:SMN Complex Proteins; D025801:Ubiquitin; D064173:Anaphase-Promoting Complex-Cyclosome