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Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092
Published on: October 2, 2017
Solution NMR structure of selenium-binding protein from Methanococcus vannielii.
Motoshi Suzuki1, Duck-Yeon Lee, Nwakaego Inyamah
1Laboratory of Molecular Biophysics, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA.
The Journal of Biological Chemistry
|July 25, 2008
Summary
Selenium is vital for cell health, but excess is toxic. Methanococcus vannielii uses selenium-binding protein (SeBP) to regulate selenium transport, though its structure suggests a need for specific precursors for optimal binding.
Area of Science:
- Biochemistry
- Structural Biology
- Microbiology
Background:
- Selenium is an essential nutrient, crucial for enzyme function, but toxic at high concentrations.
- Dysregulation of selenium levels can lead to cellular abnormalities and disease.
- In Methanococcus vannielii, selenium transport is mediated by selenium-binding protein (SeBP).
Purpose of the Study:
- To elucidate the solution structure of Methanococcus vannielii SeBP.
- To understand the mechanism of selenium transport and regulation by SeBP.
- To identify factors influencing selenium binding to SeBP.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy was used to determine the solution structure of SeBP.
- Analysis of subunit composition and oligomeric state (symmetric pentamer of 8.8-kDa subunits).
- Investigation of the structural features, including secondary structures (alpha-helix and beta-sheet) and inter-subunit interactions (hydrophobic and hydrogen bonds).
Main Results:
- The solution structure of SeBP revealed a pentameric assembly of subunits, each with an alpha-helix and a 4-stranded beta-sheet.
- Subunit stability is primarily due to hydrophobic interactions, supplemented by hydrogen bonds.
- A flexible loop containing Cys(59), critical for selenium binding, exhibits restricted accessibility in the determined structure.
Conclusions:
- SeBP effectively sequesters selenium, regulating intracellular free selenium levels and delivering it to selenophosphate synthase.
- The restricted accessibility of Cys(59) suggests that specific selenium precursors or additional factors may be required to facilitate loop opening for efficient selenium binding.
- Understanding SeBP structure provides insights into selenium homeostasis mechanisms in extremophilic archaea.
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