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Functional Characterization of RING-Type E3 Ubiquitin Ligases In Vitro and In Planta
Published on: December 5, 2019
Active site remodelling accompanies thioester bond formation in the SUMO E1
Shaun K Olsen1, Allan D Capili, Xuequan Lu
1Structural Biology, Sloan-Kettering Institute, New York, New York 10065, USA.
Nature
|February 19, 2010
Summary
This study reveals the structural mechanisms behind E1 enzyme activation of SUMO proteins. Crystal structures show how the E1 enzyme remodels its catalytic domain to form crucial thioester bonds.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biology
Background:
- E1 enzymes are essential for activating ubiquitin (Ub) and ubiquitin-like (Ubl) proteins through a two-step process.
- This process involves carboxy-terminal adenylation and thioester bond formation with a catalytic cysteine residue.
- The structural basis for these critical intermediates in E1 enzyme function has remained largely unknown.
Purpose of the Study:
- To elucidate the structural mechanisms underlying E1 enzyme-mediated activation of SUMO (Small Ubiquitin-like Modifier) proteins.
- To provide high-resolution structural insights into the adenylation and thioester bond formation intermediates.
Main Methods:
- X-ray crystallography was employed to determine the structures of human SUMO E1.
- Complexes with SUMO adenylate and tetrahedral intermediate analogues were analyzed at 2.45 and 2.6 Å resolution.
- Mutational analyses and biochemical assays were performed to validate the functional significance of observed structural changes.
Main Results:
- Crystal structures reveal the dynamic repositioning of the E1 catalytic cysteine domain during thioester bond formation.
- A significant 130-degree rotation of the Cys domain occurs after adenylation, driven by the release of side chain contacts to ATP.Mg.
- Key structural elements, including helices and loops involved in catalysis, undergo substantial remodeling, facilitating the transition from adenylation to thioester bond formation.
Conclusions:
- The study provides the first structural evidence for the dynamic conformational changes in E1 enzymes during SUMO activation.
- These findings explain how E1 enzymes switch from adenylation to thioester bond formation through domain rotation and structural remodeling.
- The identified mechanisms are likely conserved across different E1 enzymes, offering a general model for Ub/Ubl activation.
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