Structure of the B-DNA Oligomers d(CGCTAGCG) and d(CGCTCTAGAGCG) in New Crystal Forms

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• 作者：Valya Tereshko ; Lourdes Urpí ; Lucy Malinina ; Tam Huynh-Dinh ; and Juan A. Subirana
• 刊名：Biochemistry
• 出版年：1996
• 出版时间：September 10, 1996
• 年：1996
• 卷：35
• 期：36
• 页码：11589 - 11595
• 全文大小：325K
• 年卷期：v.35,no.36(September 10, 1996)
• ISSN：1520-4995

文摘

We present the structure of the dodecamer CGCTCTAGAGCG and therelated octamerCGCTAGCG, both in the B form, determined by single crystal X-raydiffraction. Two different crystalforms of the octamer have been obtained, with either three or fourduplexes in the asymmetric unit. Thedodecamer crystallizes in the P2₁ space groupwith two duplexes in the asymmetric unit. Very fewsuchstructures have been previously reported, while the octamer structureis the first one determined withthree duplexes in the asymmetric unit. It is also the firstoctamer with standard Watson-Crick base pairsto be crystallized in the B form. The crystal structure isstabilized in both cases by interactions betweenthe guanines in the two terminal base pairs of each duplex. Thisinteraction is similar to that found inmost dodecamers which have been previously studied, but here it isfound in a new unit cell (for thedodecamer) and in one octamer. In the dodecamer cytosine-stackinginteractions between neighbor duplexesare also present. The two dodecamer duplexes in the asymmetricunit show different patterns of bending,while the octamer molecule has a rather straight helical axis. Theresults presented confirm the strongconformational variability of the TA pyrimidine-purine step anddemonstrate a clear alternating structurefor the (CT/GA)_n sequence.