The potentially Z-DNA-forming sequence d(GTGTACAC) crystallizes as A-DNA.
(GT)n/(CA)n sequences have stimulated much interest because of their frequent occurrence in eukaryotic DNA and their potential for forming the left-handed Z-DNA structure. We here report the X-ray crystal structure of a self-complementary octadeoxynucleotide, d(GTGTACAC), at 2.5 A resolution. The molecule adopts a right-handed double-helical conformation belonging to the A-DNA family. In this alternating purine-pyrimidine DNA minihelix the roll and twist angles show alternations qualitatively consistent with Calladine's rules. The average tilt angle of 9.3 degrees is between the values found in A-DNA (19 degrees) and B-DNA (-6 degrees) fibers. It is envisaged that such intermediate conformations may render diversity to genomic DNA. The base-pair tilt angles and the base-pair displacements from the helix axis are found to be correlated for the known A-DNA double-helical fragments.
Jain
S
S
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison 53706.
Zon
G
G
Sundaralingam
M
M
D001483:Base Sequence; D003460:Crystallization; D004247:DNA; D008958:Models, Molecular; D009838:Oligodeoxyribonucleotides; D014961:X-Ray Diffraction
D009838:Oligodeoxyribonucleotides; D004247:DNA