Selenium derivatization of nucleic acids for crystallography.

Area of Science:

• Structural Biology
• Biochemistry
• Crystallography

Background:

• Determining high-resolution nucleic acid structures is crucial for understanding biological function.
• Conventional methods like bromine derivatization can alter DNA structure and require lengthy crystallization times.
• Developing efficient and non-perturbing derivatization techniques is essential for advancing structural studies.

Purpose of the Study:

• To investigate selenium (Se) derivatization as an alternative to bromine (Br) derivatization for DNA X-ray crystallography.
• To compare the effects of Se and Br derivatization on DNA structure, crystal growth, and diffraction quality.
• To assess the utility of Se derivatization for phasing and high-quality crystal formation.

Main Methods:

• High-resolution X-ray crystallography was employed to determine the structures of native, selenium-derivatized, and bromine-derivatized DNA.
• MAD and SAD phasing techniques were used for structure determination of the selenium-derivatized DNA.
• Comparative analysis of structural parameters, crystal growth rates, and diffraction patterns was performed.

Main Results:

• Selenium derivatization at the 2'-position of T2 resulted in a 1.28 A resolution structure, isomorphous to the native DNA (2.0 A).
• Bromine incorporation at the 5-position of T4 altered local backbone torsion angles and solvent hydration patterns.
• Se-derivatized DNA crystallized overnight with high-diffraction quality, significantly faster than native and Br-derivatized DNA, and under broader buffer conditions.

Conclusions:

• Selenium derivatization facilitates high-quality DNA crystal growth and can accelerate the crystallization process.
• Se derivatization is a viable alternative to Br derivatization, potentially minimizing structural perturbations.
• This technique enhances the efficiency and success rate of nucleic acid X-ray crystal structure determination.