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Isolation and physical characterization of random insertions in Staphylococcal nuclease
1Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD, 21218, USA.
Journal of Molecular Biology
|September 23, 1998
Summary
Genetic engineering created internal tandem duplications in Staphylococcal nuclease, altering protein activity and stability. Some mutants showed partial unfolding, impacting protein structure and function.
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Engineering
Background:
- Staphylococcal nuclease is a well-studied enzyme.
- Understanding protein structure-function relationships is crucial.
- Internal tandem duplications can alter protein properties.
Purpose of the Study:
- To investigate the effects of internal tandem duplications on Staphylococcal nuclease.
- To characterize the physical and functional consequences of these genetic modifications.
Main Methods:
- Genetic engineering to introduce random internal tandem duplications.
- Enzyme activity assays.
- Circular dichroism and size exclusion chromatography for structural analysis.
- Guanidine hydrochloride denaturation for stability assessment.
Main Results:
- Generated insertion mutants with varying Staphylococcal nuclease activities (0.1% to 1/2000 of wild-type).
- Insertions occurred in both structured and unstructured regions.
- Proteins remained folded and monomeric, with one exception showing partial unfolding.
- Stability varied, with some mutants destabilized by up to 4 kcal/mol.
Conclusions:
- Internal tandem duplications can be introduced into Staphylococcal nuclease with diverse effects on activity and stability.
- Protein folding and monomeric state are generally maintained, but stability can be compromised.
- The location of insertions (structured vs. unstructured regions) does not solely determine the functional outcome.