Five enzymes of the Arg/N-degron pathway form a targeting complex: The concept of superchanneling
- 19 May 2020
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences of the United States of America
- Vol. 117 (20), 10778-10788
- https://doi.org/10.1073/pnas.2003043117
Abstract
The Arg/N-degron pathway targets proteins for degradation by recognizing their N-terminal (Nt) residues. If a substrate bears, for example, Nt-Asn, its targeting involves deamidation of Nt-Asn, arginylation of resulting Nt-Asp, binding of resulting (conjugated) Nt-Arg to the UBR1-RAD6 E3-E2 ubiquitin ligase, ligase-mediated synthesis of a substrate-linked polyubiquitin chain, its capture by the proteasome, and substrate's degradation. We discovered that the human Nt-Asn-specific Nt-amidase NTAN1, Nt-Gln-specific Nt-amidase NTAQ1, arginyltransferase ATE1, and the ubiquitin ligase UBR1-UBE2A/B (or UBR2-UBE2A/B) form a complex in which NTAN1 Nt-amidase binds to NTAQ1, ATE1, and UBR1/UBR2. In addition, NTAQ1 Nt-amidase and ATE1 arginyltransferase also bind to UBR1/UBR2. In the yeast Saccharomyces cerevisiae, the Nt-amidase, arginyltransferase, and the double-E3 ubiquitin ligase UBR1-RAD6/UFD4-UBC4/5 are shown to form an analogous targeting complex. These complexes may enable substrate channeling, in which a substrate bearing, for example, Nt-Asn, would be captured by a complex-bound Nt-amidase, followed by sequential Nt modifications of the substrate and its polyubiquitylation at an internal Lys residue without substrate's dissociation into the bulk solution. At least in yeast, the UBR1/UFD4 ubiquitin ligase interacts with the 26S proteasome, suggesting an even larger Arg/N-degron-targeting complex that contains the proteasome as well. In addition, specific features of protein-sized Arg/N-degron substrates, including their partly sequential and partly nonsequential enzymatic modifications, led us to a verifiable concept termed "superchanneling." In superchanneling, the synthesis of a substrate-linked poly-Ub chain can occur not only after a substrate's sequential Nt modifications, but also before them, through a skipping of either some or all of these modifications within a targeting complex.Funding Information
- HHS | NIH | National Institute of General Medical Sciences (GM031530)
- HHS | NIH | National Institute of Diabetes and Digestive and Kidney Diseases (DK039520)
This publication has 111 references indexed in Scilit:
- The N-end rule pathway counteracts cell death by destroying proapoptotic protein fragmentsProceedings of the National Academy of Sciences of the United States of America, 2012
- The N‐end rule pathway and regulation by proteolysisProtein Science, 2011
- Defining the geometry of the two-component proteasome degronNature Chemical Biology, 2011
- The N-end rule pathway is mediated by a complex of the RING-type Ubr1 and HECT-type Ufd4 ubiquitin ligasesNature, 2010
- Ubr1 and Ubr2 Function in a Quality Control Pathway for Degradation of Unfolded Cytosolic ProteinsMolecular Biology of the Cell, 2010
- N-Terminal Acetylation of Cellular Proteins Creates Specific Degradation SignalsScience, 2010
- Glutamine-Specific N-Terminal Amidase, a Component of the N-End Rule PathwayMolecular Cell, 2009
- Amino Acids Induce Peptide Uptake via Accelerated Degradation of CUP9, the Transcriptional Repressor of the PTR2 Peptide TransporterPublished by Elsevier BV ,2008
- Tryptophan synthase: the workings of a channeling nanomachineTrends in Biochemical Sciences, 2008
- The N-end rule is mediated by the UBC2(RAD6) ubiquitin-conjugating enzyme.Proceedings of the National Academy of Sciences of the United States of America, 1991