DNA polymorphism in crystals: three stable conformations for the decadeoxynucleotide d(GCATGCATGC)

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• DNA is known to be flexible, with some sequences adopting multiple conformations.
• Previous studies have shown DNA fragments can exist in two distinct structures.

Purpose of the Study:

• To present the first example of a DNA fragment adopting three distinct conformations in crystals.
• To investigate the conformational flexibility of the decanucleotide d(GCATGCATGC).

Main Methods:

• X-ray crystallography was used to determine high-resolution DNA structures.
• Circular Dichroism (CD) spectra were recorded during titration with metal ions and spermine.

Main Results:

• The decanucleotide d(GCATGCATGC) was observed to adopt three distinct conformations: a double-fold structure, a B-type double-helical structure, and an A-type double-helical structure.
• One crystal contained both the double-fold and B-type structures simultaneously.
• CD spectra suggest the molecule exists as a mixed population of structures in solution, influenced by environmental factors like metal ion concentration.

Conclusions:

• DNA's ability to adopt multiple conformations is further exemplified.
• Environmental conditions play a crucial role in determining DNA structure.
• DNA may alter its structure to accommodate binding with proteins or drugs.