1ue3
From Proteopedia
Crystal structure of d(GCGAAAGC) containing hexaamminecobalt
Overview
A DNA fragment d(GCGAAAGC), postulated to adopt a stable mini-hairpin structure on the basis of its extraordinary properties, has been X-ray analyzed. Two octamers related by a crystallographic twofold symmetry are aligned in an antiparallel fashion and associate to form a duplex, which is maintained by two Watson-Crick G.C base pairs and a subsequent sheared G.A pair at both ends. The central two A residues are free from base-pair formation. The corresponding base moieties of the two strands are intercalated and stacked on each other, forming a long column of G(1)-C(2)-G(3)-A(4)-A(5)(*)-A(5)-A(4)(*)-G(3)(*)-C(2)(*)-G(1)(*) (asterisks indicate the counter-strand). The Watson-Crick and major-groove sites of the four stacked adenine bases are exposed to the solvent region, suggesting a functional role. Since this structural motif is similar to those found in the nonamers d(G(Br)CGAAAGCT) and d(G(I)CGAAAGCT), the base-intercalated duplex may be a stable form of the specific sequence. Electrophoresis results suggest that the octamer has two states, monomeric and dimeric, in solution depending on the Mg(2+) concentration. The present duplex is preferred under the crystallization conditions, which correspond to physiologically allowed conditions.
About this Structure
Full crystallographic information is available from OCA.
Reference
Structure of d(GCGAAAGC) (hexagonal form): a base-intercalated duplex as a stable structure., Sunami T, Kondo J, Hirao I, Watanabe K, Miura KI, Takenaka A, Acta Crystallogr D Biol Crystallogr. 2004 Jan;60(Pt 1):90-6. Epub 2003 Dec, 18. PMID:14684897 Page seeded by OCA on Sat May 3 11:05:32 2008
