A combinatorial histidine scanning library approach to engineer highly pH-dependent protein switches
Megan L Murtaugh1, Sean W Fanning, Tressa M Sharma
1Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL 60115, USA.
Protein Science : a Publication of the Protein Society
|July 19, 2011
Summary
Researchers engineered novel protein switches with tunable pH sensitivity. A combinatorial approach rapidly generated antibodies with high affinity and drastically reduced binding at lower pH, enabling new applications for pH-responsive protein engineering.
Area of Science:
- Protein Engineering
- Biochemistry
- Molecular Biology
Background:
- Protein switches offer tunable function via environmental triggers.
- Engineering pH-sensitive protein interactions traditionally involves time-intensive methods and can reduce affinity.
Purpose of the Study:
- To develop a rapid and robust method for engineering highly pH-sensitive protein switches.
- To test the hypothesis that multiple ionizable groups are necessary for pH-dependent binding.
Main Methods:
- A combinatorial histidine library was created for a model VHH antibody targeting RNase A.
- Antibodies were selected for both high-affinity binding and pH-sensitivity using a dual-function in vitro strategy.
Main Results:
- Engineered antibodies retained near wild-type affinity but exhibited drastically reduced binding at lower pH.
- The incorporation of multiple histidine residues was key to achieving high pH sensitivity.
- Observed histidine "hot-spots" provide insights into ionizable residue roles in protein interfaces.
Conclusions:
- A combinatorial approach rapidly yields highly pH-sensitive protein affinity reagents.
- This method enhances the development of pH switch proteins and understanding of protein interfaces.
- The strategy is general and robust for diverse applications.
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