Radiation damage to nucleoprotein complexes in macromolecular crystallography

Area of Science:

• Structural Biology
• Biophysics
• Radiation Chemistry

Background:

• X-ray crystallography advances protein studies, but nucleic acid radiation damage is less understood.
• Direct comparison of radiation damage in protein and DNA is difficult.
• Nucleoprotein complexes offer a model for studying damage in both components simultaneously.

Purpose of the Study:

• To investigate specific X-ray radiation damage mechanisms in both protein and DNA components of a nucleoprotein complex.
• To quantitatively compare the radiation sensitivity of protein versus DNA within a biologically relevant complex.
• To develop a general computational method for analyzing radiation damage in macromolecular diffraction data.

Main Methods:

• Utilized a model protein-DNA complex (C.Esp1396I) for X-ray crystallography.
• Collected diffraction data over a wide dose range (2.07–44.63 MGy).
• Developed and applied a computational method for quantitative analysis of radiation damage sites.

Main Results:

• Observed specific damage to amino acids in the protein and bond cleavage in the DNA (base-sugar, sugar-phosphate).
• Demonstrated that DNA is significantly more resistant to X-ray damage than protein within the complex.
• Protein showed susceptibility to damage at lower doses, while DNA damage occurred only at substantially higher doses.

Conclusions:

• The study provides quantitative insights into differential radiation damage in nucleoprotein complexes.
• DNA exhibits greater resistance to X-ray induced damage compared to protein components.
• The developed computational method is broadly applicable for analyzing radiation damage in macromolecular crystallography.