Crystal structure and stability of a DNA duplex containing A(anti).G(syn) base-pairs.
The synthetic dodecanucleotide d(CGCAAATTGGCG) has been analysed by single-crystal X-ray diffraction techniques and the structure refined to R = 0.16 and 2.25 A resolution, with the location of 94 solvent molecules. The sequence crystallizes as a full turn of a B-DNA helix with ten Watson-Crick base-pairs and two adenine-guanine mispairs. The analysis clearly shows that the mismatches are of the form A(anti).G(syn). Thermal denaturation studies indicate that the stability of the duplex is strongly pH dependent, with a maximum at pH 5.0, suggesting that the base-pair is stabilized by protonation. Three different arrangements have been observed for base-pairs between guanine and adenine and it is likely that A.G mismatch conformation is strongly influenced by dipole-dipole interactions with adjacent base-pairs.
Department of Chemistry, University of Edinburgh, U.K.
T
T
Brown
G A
GA
Leonard
E D
ED
Booth
J
J
Chambers
D000225:Adenine; D001482:Base Composition; D001483:Base Sequence; D006147:Guanine; D008969:Molecular Sequence Data; D009711:Nucleotides; D014961:X-Ray Diffraction
D009711:Nucleotides; D006147:Guanine; D000225:Adenine