Crystal structure of d(GCGAAAGCT) containing a parallel-stranded duplex with homo base pairs and an anti-parallel duplex with Watson-Crick base pairs.
Nucleic Acids Res
; 30(23): 5253-60, 2002 Dec 01.
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| ID: mdl-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, C2C2+ (singly-protonated between the Watson- Crick sites), G3G3 (between the minor groove sites), A4A4 (between the major groove sites) and A5A5 (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.
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Modelos Moleculares
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2002
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Article