title: Crystal structure of d(GCGAAAGCT) containing a parallel-stranded duplex with homo base pairs and an anti-parallel duplex with Watson-Crick base pairs.
abstract: A DNA fragment d(GCGAAAGCT), known to adopt a stable mini-hairpin structure in solution, has been crystallized in the space group I4(1)22 with the unit-cell dimensions a = b = 53.4 A and c = 54.0 A, and the crystal structure has been determined at 2.5 A resolution. The four nucleotide residues CGAA of the first half of the oligomer form a parallel duplex with another half through the homo base pairs, C2:C2+ (singly-protonated between the Watson- Crick sites), G3:G3 (between the minor groove sites), A4:A4 (between the major groove sites) and A5:A5 (between the Watson-Crick sites). The two strands remaining in the half of the parallel duplex are split away in different directions, and they pair in an anti-parallel B-form duplex with the second half extending from a neighboring parallel duplex, so that an infinite column is formed in a head-to-tail fashion along the c-axis. It seems that a hexa-ammine cobalt cation supports such a branched and bent conformation of the oligomer. One end of the parallel duplex is stacked on the corresponding end of the adjacent parallel duplex; between them, the guanine base of the first residue is stacked on the fourth ribose of another duplex.
authors.affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Sunami
authors.forename: Jiro
authors.initials: J
authors.lastname: Kondo
authors.forename: Tomonori
authors.initials: T
authors.lastname: Kobuna
authors.forename: Ichiro
authors.initials: I
authors.lastname: Hirao
authors.forename: Kimitsuna
authors.initials: K
authors.lastname: Watanabe
authors.forename: Kin-ichiro
authors.initials: K
authors.lastname: Miura
authors.forename: Akio
authors.initials: A
authors.lastname: Takénaka
mesh_terms: D020029:Base Pairing; D001483:Base Sequence; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry*; D006860:Hydrogen Bonding; D007477:Ions; D008958:Models, Molecular; D015394:Molecular Structure; D009690:Nucleic Acid Conformation; D009692:Nucleic Acid Heteroduplexes / Q000737:chemistry
chemical_list: D007477:Ions; D009692:Nucleic Acid Heteroduplexes; D004247:DNA