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Protein thermostability above 100 degreesC: a key role for ionic interactions
C Vetriani1, D L Maeder, N Tolliday
1Center of Marine Biotechnology, University of Maryland Biotechnology Institute, 701 E. Pratt Street, Baltimore, MD 21202, USA.
Summary
Multisubunit enzymes from hyperthermophiles can withstand extreme heat. Enhancing intersubunit ion-pair networks through specific mutations significantly improved enzyme thermostability without affecting catalysis.
Area of Science:
- Biochemistry
- Structural Biology
- Enzyme Engineering
Background:
- Hyperthermophilic microorganisms possess enzymes stable at temperatures exceeding 100°C.
- Multisubunit enzymes are crucial in biological systems and their thermostability is of great interest.
Purpose of the Study:
- To identify key stabilizing features in hexameric glutamate dehydrogenases from hyperthermophiles.
- To investigate the role of intersubunit interactions in enzyme thermostability.
Main Methods:
- Homology-based modeling and direct structure comparison of glutamate dehydrogenases.
- Site-directed mutagenesis to alter specific residues and restore ion-pair interactions.
- Thermal stability assays at 104°C and assessment of catalytic properties.
Main Results:
- A 16-fold difference in thermal stability was observed between homologous enzymes from Pyrococcus furiosus and Thermococcus litoralis.
- Reduced intersubunit ion-pair networks in the less stable enzyme were identified.
- Dual mutations restoring ion-pair interactions yielded a fourfold improvement in thermostability at 104°C, while single mutations were detrimental.
- Catalytic activity remained unaffected by the mutations.
Conclusions:
- Extensive intersubunit ion-pair networks are a viable strategy for enhancing multisubunit enzyme thermostability.
- The local environment of residues plays a critical role in determining their impact on protein stability.
- This study provides insights into engineering thermostable enzymes for industrial and biotechnological applications.