Mechanism of ubiquitin ligation and lysine prioritization by a HECT E3.

Publication Type:

Journal Article

Source:

Elife, Volume 2, p.e00828 (2013)

Keywords:

Amino Acid Sequence, Catalytic Domain, Lysine, Molecular Sequence Data, Mutagenesis, Protein Conformation, Sequence Homology, Amino Acid, Ubiquitin, Ubiquitin-Protein Ligases

Abstract:

<p>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. </p>

PDB: 
4LCD
Detector: 
Q315
Beamline: 
24-ID-C