Structural insights into Ubr1-mediated N-degron polyubiquitination.
The N-degron pathway targets proteins that bear a destabilizing residue at the N terminus for proteasome-dependent degradation1. In yeast, Ubr1-a single-subunit E3 ligase-is responsible for the Arg/N-degron pathway2. How Ubr1 mediates the initiation of ubiquitination and the elongation of the ubiquitin chain in a linkage-specific manner through a single E2 ... ubiquitin-conjugating enzyme (Ubc2) remains unknown. Here we developed chemical strategies to mimic the reaction intermediates of the first and second ubiquitin transfer steps, and determined the cryo-electron microscopy structures of Ubr1 in complex with Ubc2, ubiquitin and two N-degron peptides, representing the initiation and elongation steps of ubiquitination. Key structural elements, including a Ubc2-binding region and an acceptor ubiquitin-binding loop on Ubr1, were identified and characterized. These structures provide mechanistic insights into the initiation and elongation of ubiquitination catalysed by Ubr1.
Mesh Terms:
Binding Sites, Biocatalysis, Cryoelectron Microscopy, Lysine, Models, Molecular, Proteasome Endopeptidase Complex, Proteolysis, Reproducibility of Results, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Ubiquitin, Ubiquitin-Conjugating Enzymes, Ubiquitin-Protein Ligases, Ubiquitination
Binding Sites, Biocatalysis, Cryoelectron Microscopy, Lysine, Models, Molecular, Proteasome Endopeptidase Complex, Proteolysis, Reproducibility of Results, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Ubiquitin, Ubiquitin-Conjugating Enzymes, Ubiquitin-Protein Ligases, Ubiquitination
Nature
Date: Dec. 01, 2020
PubMed ID: 34789879
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