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Coupling protein stability and protein function in Escherichia coli CspA
B J Hillier1, H M Rodriguez, L M Gregoret
1Department of Chemistry and Biochemistry, University of California, USA.
Folding & Design
|May 5, 1998
Summary
The aromatic cluster in CspA protein is crucial for binding single-stranded nucleic acids and maintaining protein stability. Mutations to this cluster impair DNA binding and surprisingly reduce protein stability, especially when mutated to serine.
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Science
Background:
- CspA is a small protein that binds single-stranded RNA and DNA.
- Its binding site features a large nonpolar patch of aromatic amino acids, unusual for protein surfaces.
- This feature may compromise protein stability for nucleic acid binding.
Purpose of the Study:
- To investigate the role of the aromatic cluster in CspA's DNA binding and protein stability.
- To understand the structure-function relationship of aromatic-rich binding sites in nucleic acid-binding proteins.
Main Methods:
- Site-directed mutagenesis of three key phenylalanine residues in CspA.
- Assessing the impact of single and combined mutations (to leucine and serine) on DNA binding affinity.
- Evaluating the effect of these mutations on protein stability.
Main Results:
- All mutations to the aromatic cluster adversely affected DNA binding.
- Mutations, particularly those to serine, significantly destabilized the CspA protein.
- The aromatic cluster is essential for both CspA's function and structural integrity.
Conclusions:
- The aromatic cluster in CspA is indispensable for both its nucleic acid binding function and overall protein stability.
- Findings are relevant for designing stable beta-sheet proteins and single-stranded nucleic acid-binding proteins.
- Suggests aromatic-aromatic intercalation as a potential binding mode for such proteins.