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In Vitro Directed Evolution of a Restriction Endonuclease with More Stringent Specificity
Published on: March 25, 2020
Solution parameters modulating DNA binding specificity of the restriction endonuclease EcoRV.
Nina Y Sidorova1, Shakir Muradymov, Donald C Rau
1Laboratory of Physical and Structural Biology, Program of Physical Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-0924, USA. sidorova@mail.nih.gov
The FEBS Journal
|June 1, 2011
Summary
Restriction endonucleases like EcoRV distinguish specific DNA sequences. Binding stringency is modulated by water activity and pH, not just divalent ions, impacting cellular function.
Area of Science:
- Molecular Biology
- Biochemistry
- Structural Biology
Background:
- Restriction endonucleases play a vital role in DNA binding specificity.
- EcoRV crystal structures reveal differences in specific and non-cognate complexes, suggesting varied hydration and binding energies.
- Previous studies at optimal pH (7.5) showed minimal differences in EcoRV binding to specific vs. non-specific DNA without divalent ions.
Purpose of the Study:
- To investigate the influence of water activity, pH, and salt concentration on EcoRV DNA binding stringency.
- To measure EcoRV-DNA competitive binding in the absence of divalent ions using a self-cleavage assay.
- To evaluate how cellular conditions affect the enzyme's ability to discriminate between DNA sequences.
Main Methods:
- Utilized a self-cleavage assay to quantify EcoRV-DNA competitive binding.
- Systematically varied water activity (neutral solute concentration), pH, and salt concentration.
- Analyzed binding constants for specific and non-specific DNA sequences in the absence of divalent ions.
Main Results:
- EcoRV demonstrates a strong ability to differentiate between specific and non-specific DNA sequences.
- Specific-nonspecific binding affinity increases significantly with higher neutral solute concentrations and lower pH.
- Observed differences in water association with specific and non-specific DNA-EcoRV complexes align with structural data.
- Osmotic pressure dependence suggests dilute solution binding measurements may not directly translate to crowded cellular environments.
Conclusions:
- Water activity and pH are critical factors, alongside divalent ions, in modulating EcoRV binding specificity.
- The findings highlight the importance of considering cellular environmental factors for accurate interpretation of protein-DNA interactions.
- Understanding these modulations is key for comprehending the precise function of restriction enzymes in vivo.
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