Arabidopsis thaliana dehydroascorbate reductase 2: Conformational flexibility during catalysis
Nandita Bodra1,2,3,4,5, David Young1,2,3, Leonardo Astolfi Rosado1,2,3
1Center for Structural Biology, VIB, 1050 Brussels, Belgium.
Scientific Reports
|February 15, 2017
Summary
Dehydroascorbate reductase (DHAR) regenerates ascorbic acid, a key plant antioxidant. Structural analysis reveals how it binds glutathione (GSH) and releases oxidized glutathione (GSSG), explaining its unique function.
Area of Science:
- Biochemistry
- Plant Physiology
- Structural Biology
Background:
- Dehydroascorbate reductase (DHAR) is crucial for regenerating ascorbic acid, a vital plant antioxidant.
- DHAR enzymes are structurally similar to glutathione transferases (GSTs) but possess distinct catalytic activity.
- A catalytic cysteine residue is essential for DHAR enzyme function.
Purpose of the Study:
- To elucidate the structural basis of DHAR2 activity in Arabidopsis thaliana.
- To understand the mechanism of glutathione (GSH) binding and oxidized glutathione (GSSG) release.
- To investigate the conformational flexibility of DHAR2.
Main Methods:
- X-ray crystallography of DHAR2 with bound GSH.
- Kinetic analysis of the enzymatic mechanism.
- Normal mode analysis for conformational flexibility.
Main Results:
- The crystal structure of DHAR2 with GSH bound to the catalytic cysteine was determined.
- Localized conformational differences distinguish DHAR2 from DHAR1.
- The step of oxidized glutathione (GSSG) release was identified.
- Subdomain mobility in DHAR2 is linked to GSH binding and GSSG release.
Conclusions:
- The structure of GSH-bound DHAR2 provides insights into its catalytic mechanism.
- Conformational flexibility plays a role in DHAR2's enzymatic cycle.
- Understanding DHAR2 function is key to plant oxidative stress defense.
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