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Mechanism of ubiquitin ligation and lysine prioritization by a HECT E3
Journal article   Open access   Peer reviewed

Mechanism of ubiquitin ligation and lysine prioritization by a HECT E3

Hari B Kamadurai, Yu Qiu, Alan Deng, Joseph S Harrison, Chris Macdonald, Marcelo Actis, Patrick Rodrigues, Darcie J Miller, Judith Souphron, Steven M Lewis, …
eLife, Vol.2, pp.e00828-e00828
08/08/2013
DOI: 10.7554/eLife.00828
PMCID: PMC3738095
PMID: 23936628
url
https://doi.org/10.7554/eLife.00828View
Published (Version of record) Open Access

Abstract

Ubiquitination by HECT E3 enzymes regulates myriad processes, including tumor suppression, transcription, protein trafficking, and degradation. HECT E3s use a two-step mechanism to ligate ubiquitin to target proteins. The first step is guided by interactions between the catalytic HECT domain and the E2∼ubiquitin intermediate, which promote formation of a transient, thioester-bonded HECT∼ubiquitin intermediate. Here we report that the second step of ligation is mediated by a distinct catalytic architecture established by both the HECT E3 and its covalently linked ubiquitin. The structure of a chemically trapped proxy for an E3∼ubiquitin-substrate intermediate reveals three-way interactions between ubiquitin and the bilobal HECT domain orienting the E3∼ubiquitin thioester bond for ligation, and restricting the location of the substrate-binding domain to prioritize target lysines for ubiquitination. The data allow visualization of an E2-to-E3-to-substrate ubiquitin transfer cascade, and show how HECT-specific ubiquitin interactions driving multiple reactions are repurposed by a major E3 conformational change to promote ligation. DOI:http://dx.doi.org/10.7554/eLife.00828.001.
Mutagenesis Amino Acid Sequence Catalytic Domain Lysine - metabolism Molecular Sequence Data Protein Conformation Sequence Homology, Amino Acid Ubiquitin - chemistry Ubiquitin - metabolism Ubiquitin-Protein Ligases - chemistry Ubiquitin-Protein Ligases - genetics Ubiquitin-Protein Ligases - metabolism

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