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Generating isomorphous heavy-atom derivatives by a quick-soak method. Part II: phasing of new structures
1Structural Immunology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12441 Parklawn Drive, Rockville, MD 20852, USA. psun@nih.gov
Summary
A novel quick-soak method rapidly generates heavy-atom derivatives for protein structure determination. This approach improves crystal quality and phasing, accelerating structural genomics research.
Area of Science:
- Structural Biology
- Biophysics
- Crystallography
Background:
- De novo heavy-atom phasing is crucial for determining protein structures.
- Conventional heavy-atom searches are time-consuming and can lead to crystal damage.
Purpose of the Study:
- To introduce and validate a quick-soak method for generating heavy-atom derivatives.
- To assess the efficiency and effectiveness of quick-soaking for protein crystallography.
Main Methods:
- Application of a quick-soak method (10 min) using heavy atom solutions (HgCl2, K2PtCl4).
- Structure determination of Type II Transforming Growth Factor Beta Receptor (TBRII) and NKG2D-ULBP3 complex.
- Comparison of quick-soak derivatives with conventional long-soak derivatives.
- Analysis of derivative isomorphism and electron-density map quality.
Main Results:
- Quick-soaking successfully generated adequate phasing for TBRII structure determination.
- Shorter soak times (10 min) yielded derivatives more isomorphous to native crystals than longer soaks.
- Overnight soaks disrupted the crystal lattice for NKG2D-ULBP3, while quick soaks preserved diffraction.
- Quick-soaked K2PtCl4 derivative for NKG2D-ULBP3 resulted in a superior electron-density map.
Conclusions:
- The quick-soak method accelerates heavy-atom derivative generation for protein crystallography.
- This method preserves crystal integrity and improves phasing statistics, especially for fragile crystals.
- Quick-soaking has the potential to revolutionize structural genomics by enabling 'on-the-fly' derivatization.