Three-dimensional structures of bulge-containing DNA fragments

Area of Science:

• Structural Biology
• Molecular Biology
• Biochemistry

Background:

• DNA structure is typically a double helix.
• Bulges can occur in DNA, but their structural impact is not fully understood.

Purpose of the Study:

• To determine the three-dimensional structure of a DNA tridecamer with bulged adenine bases.
• To understand how these bulges affect DNA stability and conformation.

Main Methods:

• Single crystal X-ray diffraction at 120 K to 2.6 A resolution.
• Crystallography of a heavy-atom derivative to confirm the structure.
• X-ray diffraction of a proflavin-soaked crystal at 3.2 A resolution.

Main Results:

• A B-DNA type double helix with one looped-out and one stacked-in adenine bulge.
• The bulges form a stabilized A:A reversed Hoogsteen base-pair.
• Minimal disruption of base stacking interactions around the bulges.
• The DNA double helix exhibits flexibility and resiliency.

Conclusions:

• The DNA molecule can accommodate significant structural perturbations like bulges with minimal disruption.
• The stabilized bulges contribute to the overall stability of the DNA duplex.