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Single mutations outside the active site affect the substrate specificity in a β-glycosidase
Lúcio M F Mendonça1, Sandro R Marana
1Departamento de Bioquimica, Universidade de Sao Paulo, Sao Paulo, Brazil.
Biochimica Et Biophysica Acta
|September 17, 2011
Summary
Mutations in beta-glycosidase Sfβgly alter substrate specificity by affecting contact pathways. These pathways transmit effects from distant sites to the active site, influencing enzyme preference for beta-d-fucoside versus beta-d-glucoside.
Area of Science:
- Enzymology
- Protein Engineering
- Biochemistry
Background:
- Beta-glycosidases are crucial enzymes with diverse applications.
- Understanding enzyme specificity is key to protein engineering.
- Sfβgly is a beta-glycosidase whose substrate specificity can be modulated.
Purpose of the Study:
- To identify mutations in Sfβgly that alter substrate specificity.
- To elucidate the mechanisms by which these mutations affect enzyme activity.
- To explore the role of 'contact pathways' in propagating mutational effects.
Main Methods:
- Random mutagenesis of Sfβgly and screening for altered substrate specificity.
- Enzyme kinetics assays to quantify substrate preference (kcat/Km ratios).
- Structural modeling and analysis of residue interaction networks (contact pathways).
- Spectroscopic methods (tryptophan fluorescence, acrylamide quenching) to assess protein structure and stability.
Main Results:
- Ten mutations were identified, with most located away from the active site.
- Mutations significantly altered substrate specificity, broadening or narrowing preference.
- Structural modeling revealed 'contact pathways' connecting mutations to active site residues.
- Mutations on the same pathway exhibited similar effects on specificity and structural stability.
Conclusions:
- Mutational effects on Sfβgly substrate specificity are mediated by 'contact pathways'.
- These pathways transmit signals from distant residues to the active site, altering substrate binding and catalysis.
- The findings provide insights into enzyme engineering and structure-function relationships.
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