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Conformational Dynamics Modulate Activation of the Ubiquitin Conjugating Enzyme Ube2g2
Pearl Magala1, William E Bocik1, Ananya Majumdar1
1Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, 21218 Baltimore, Maryland, United States.
ACS Omega
|September 9, 2017
Summary
The E3 ligase gp78
Area of Science:
- Biochemistry
- Molecular Biology
- Cellular Biology
Background:
- Ube2g2 and gp78 form lysine-48 polyubiquitin chains for protein degradation.
- This process targets misfolded endoplasmic reticulum proteins for proteasomal degradation.
Purpose of the Study:
- To investigate the role of the gp78 RING domain in activating Ube2g2 ubiquitin conjugating enzyme.
- To understand the conformational dynamics of Ube2g2 during ubiquitin conjugation.
Main Methods:
- NMR spectroscopy was used to study Ube2g2 conformation.
- Single-turnover diubiquitin formation assays assessed catalytic activity.
Main Results:
- gp78-RING binding shifts Ube2g2∼Ub conjugates to a closed, active conformation.
- Mutations in the ubiquitin hydrophobic patch disrupt the closed state and affect catalytic activity.
- Conformational dynamics of Ube2g2’s active site are crucial for ubiquitin ligation.
Conclusions:
- Ube2g2’s active site conformation is rate-limiting for ubiquitin ligation.
- Dynamic flux and conformational stabilization by gp78 are key to Ube2g2 function.
- Specific K48-polyubiquitin chain elongation may prevent unproductive catalysis.
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