RNA protects a nucleoprotein complex against radiation damage.

Area of Science:

• Structural Biology
• Biophysics
• Crystallography

Background:

• Radiation damage impedes macromolecular structure determination via X-ray crystallography.
• Specific radiation damage in protein crystals is characterized, but less is known for nucleoprotein complexes.
• Understanding radiation damage is crucial for accurate biological mechanism interpretation.

Purpose of the Study:

• To develop and apply a methodology for quantifying per-atom density changes due to radiation dose in nucleoprotein complexes.
• To investigate specific radiation damage effects in the trp RNA-binding attenuation protein (TRAP) - RNA complex.
• To determine the role of RNA binding in the radiation damage susceptibility of TRAP.

Main Methods:

• Developed a methodology to quantify per-atom density changes with increasing radiation dose (1.3-25.0 MGy) at high resolution (1.98 Å).
• Studied the TRAP-RNA complex, utilizing two TRAP molecules in the asymmetric unit (one with bound RNA) for controlled investigation.
• Analyzed damage patterns in TRAP using its 11-fold symmetry for statistically significant results.

Main Results:

• RNA was significantly less susceptible to radiation-induced chemical changes than the protein component of the TRAP-RNA complex.
• RNA binding unexpectedly protected sensitive glutamate (Glu) and aspartate (Asp) residues within the TRAP molecule.
• Quantified the reduction in radiation-induced lysine (Lys) and phenylalanine (Phe) disordering upon RNA binding.

Conclusions:

• The developed methodology allows for detailed quantification of specific radiation damage in nucleoprotein complexes.
• RNA binding plays a protective role against specific radiation damage in the TRAP protein.
• These findings improve the understanding of radiation damage mechanisms in complex biological macromolecules, aiding accurate structure determination.