Left-handed double helical DNA: variations in the backbone conformation

Area of Science:

• Structural biology
• Molecular genetics
• Biochemistry

Background:

• Deoxyribonucleic acid (DNA) exists in various structural forms, including the left-handed Z-DNA and right-handed B-DNA helices.
• Understanding the conformational flexibility of DNA is essential for elucidating its biological functions and interactions.

Purpose of the Study:

• To determine the crystal structures of d(CpGpCpGpCpG) to analyze Z-DNA formation.
• To investigate the different phosphate conformations within Z-DNA and their potential roles in DNA structural transitions.

Main Methods:

• X-ray diffraction analysis was employed to solve the crystal structures of four different d(CpGpCpGpCpG) forms.
• Atomic coordinates and torsion angles were determined for the observed Z-DNA molecules.

Main Results:

• All four crystal structures revealed similar left-handed double helical Z-DNA molecules.
• Two distinct phosphate conformations were identified in the GpC sequences: one facing the helical groove and another rotated away.
• The rotated conformation was frequently observed when hydrated magnesium ions were complexed to phosphate oxygen atoms.

Conclusions:

• The observed phosphate conformations in Z-DNA may facilitate the transition between left-handed Z-DNA and right-handed B-DNA.
• The study provides detailed atomic coordinates and torsion angles for these Z-DNA structures, aiding further research.