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Stabilizing mutations and calcium-dependent stability of subtilisin.
P A Alexander1, B Ruan, S L Strausberg
1Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, 9600 Gudelsky Drive, Rockville, Maryland 20850, USA.
Biochemistry
|August 29, 2001
Summary
Stabilizing mutations in subtilisin are calcium-dependent due to conformational equilibrium. This study explains these effects and creates a hyperstable subtilisin variant.
Area of Science:
- Enzymology
- Protein Engineering
- Biochemistry
Background:
- Subtilisin stability is enhanced by mutations, but their mechanisms remain unclear.
- Stabilizing mutations often exhibit calcium-dependent effects, regardless of proximity to calcium-binding sites.
Purpose of the Study:
- To elucidate the structural and energetic basis of calcium-dependent stabilization in subtilisin mutations.
- To categorize stabilizing mutations based on their dependence on calcium or chelating agents.
Main Methods:
- Comparative analysis of mutation effects in subtilisin BPN' and calcium-free variants.
- Investigating mutations that stabilize in the presence of calcium, independently of calcium, or with chelating agents like EDTA.
Main Results:
- Stabilizing mutations are classified into three groups based on calcium dependence.
- A conformational equilibrium model (N and N* states) explains calcium-dependent stabilization.
- Mutations stabilizing in excess calcium favor the N state; those stabilizing with chelators favor the N* state.
Conclusions:
- The study provides a mechanistic explanation for calcium-dependent stabilization of subtilisin.
- A hyperstable subtilisin variant was developed, showing significantly reduced inactivation rates.
- Understanding mutation effects on conformational equilibrium aids in protein engineering for enhanced stability.