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In Vitro Analysis of E3 Ubiquitin Ligase Function
Published on: May 14, 2021
Allosteric regulation of E2:E3 interactions promote a processive ubiquitination machine
Ranabir Das1, Yu-He Liang, Jennifer Mariano
1Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, USA.
The EMBO Journal
|August 15, 2013
Summary
Ubiquitin ligase gp78 uses multiple binding sites to enhance ubiquitin transfer. This mechanism explains how low-affinity RING-E2 interactions achieve processive ubiquitination, crucial for cellular processes.
Area of Science:
- Biochemistry
- Molecular Biology
- Cellular Biology
Background:
- RING finger proteins are the main ubiquitin ligases (E3s).
- They interact with ubiquitin-conjugating enzymes (E2s) to ubiquitinate substrates.
- The mechanism linking low-affinity RING-E2 interactions to high processivity is unclear.
Purpose of the Study:
- To investigate the mechanism of processive ubiquitination mediated by the RING E3 ligase gp78.
- To elucidate the role of the G2BR domain in enhancing ubiquitination.
- To understand how gp78 facilitates efficient ubiquitin transfer.
Main Methods:
- Structural analysis of the RING:Ube2g2:G2BR complex.
- Biochemical assays to study binding affinities and ubiquitination activity.
- Investigating allosteric effects induced by G2BR and conjugated ubiquitin.
Main Results:
- The G2BR domain allosterically enhances RING:Ube2g2 binding and ubiquitination.
- A G2BR-induced conformational change at the RING:Ube2g2 interface is essential for enhanced binding.
- Ternary interaction with conjugated ubiquitin and the conformational effect are required for ubiquitin transfer.
- gp78 binding to Ube2g2 induces E2 exchange, facilitating processive ubiquitination.
Conclusions:
- gp78 functions as a ubiquitination machine with coordinated E2-binding sites.
- Allosteric regulation by G2BR and conjugated ubiquitin drives processive ubiquitination.
- This study reveals a novel mechanism for efficient ubiquitin ligase activity.
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