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Atomic resolution structures of trypsin provide insight into structural radiation damage
H K Leiros1, S M McSweeney, A O Smalås
1Protein Crystallography Group, Department of Chemistry, Faculty of Science, University of Tromsø, N-9037 Tromsø, Norway.
Summary
High-intensity synchrotron radiation causes specific radiation damage in protein crystals, breaking disulfide bonds and altering structures. This damage is linked to beamline intensity, not just total X-ray dose.
Area of Science:
- Structural biology
- Protein crystallography
- Radiation damage mechanisms
Background:
- Radiation damage is a critical issue in protein X-ray crystallography.
- Damage manifests as specific alterations like disulfide bond cleavage and increased B factors.
Purpose of the Study:
- To investigate the impact of synchrotron radiation intensity on protein crystal structure.
- To characterize radiation damage in trypsin at atomic resolution.
Main Methods:
- Collected X-ray diffraction data for two trypsin structures at atomic resolution (1.00 and 0.95 Å).
- Utilized a third-generation synchrotron (ESRF) at two distinct beamlines with varying intensities.
Main Results:
- Observed breakage of disulfide bonds in both trypsin structures, with Cys191-Cys220 being particularly sensitive.
- The dataset from the higher-intensity beamline (ID14-EH4) showed greater radiation damage, including lower cysteine occupancies and more disulfide bond breakage.
- High X-ray intensity, not solely the total dose, was identified as the primary driver of damage.
Conclusions:
- High-intensity synchrotron radiation significantly contributes to specific radiation damage in protein crystals.
- Understanding beamline intensity effects is crucial for optimizing data collection strategies in X-ray crystallography.
- Minimizing exposure to high-intensity beams can preserve crystal integrity and improve structural data quality.