PDBsum entry 1ixj

DNA

PDB id: 1ixj

Contents

DNA/RNA

Ligands

NCO

Metals

_MG ×2

Waters ×19

References listed in PDB file

Key reference

• 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.
• Authors: T.Sunami, J.Kondo, T.Kobuna, I.Hirao, K.Watanabe, K.Miura, A.Takénaka.
• Ref.: Nucleic Acids Res, 2002, 30, 5253-5260. [DOI no: 10.1093/nar/gkf639]
• PubMed id: 12466550

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.