title: Substrate degradation by the proteasome: a single-molecule kinetic analysis.
abstract: To address how the configuration of conjugated ubiquitins determines the recognition of substrates by the proteasome, we analyzed the degradation kinetics of substrates with chemically defined ubiquitin configurations. Contrary to the view that a tetraubiquitin chain is the minimal signal for efficient degradation, we find that distributing the ubiquitins as diubiquitin chains provides a more efficient signal. To understand how the proteasome actually discriminates among ubiquitin configurations, we developed single-molecule assays that distinguished intermediate steps of degradation kinetically. The level of ubiquitin on a substrate drives proteasome-substrate interaction, whereas the chain structure of ubiquitin affects translocation into the axial channel on the proteasome. Together these two features largely determine the susceptibility of substrates for proteasomal degradation.
authors: Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.
authors: Ying
authors: Y
authors: Lu
authors: Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
authors: Byung-hoon
authors: BH
authors: Lee
authors: Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
authors: Randall W
authors: RW
authors: King
authors: Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
authors: Daniel
authors: D
authors: Finley
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: D019926:Cyclin B / Q000378:metabolism; D064248:Geminin / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D059748:Proteolysis; D064249:Securin / Q000378:metabolism; D013269:Stochastic Processes; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism*; D057149:Ubiquitinated Proteins / Q000737:chemistry / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D019926:Cyclin B; D064248:Geminin; D064249:Securin; D025801:Ubiquitin; D057149:Ubiquitinated Proteins; D046988:Proteasome Endopeptidase Complex