1be5
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(New page: 200px<br /><applet load="1be5" size="450" color="white" frame="true" align="right" spinBox="true" caption="1be5" /> '''STRUCTURAL STUDIES OF A STABLE PARALLEL-STRA...)
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Revision as of 21:57, 24 November 2007
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STRUCTURAL STUDIES OF A STABLE PARALLEL-STRANDED DNA DUPLEX INCORPORATING ISOGUANINE:CYTOSINE AND ISOCYTOSINE:GUANINE BASE PAIRS BY NMR, MINIMIZED AVERAGE STRUCTURE
Overview
Isoguanine (2-hydroxyladenine) is a product of oxidative damage to DNA and, has been shown to cause mutation. It is also a potent inducer of, parallel-stranded DNA duplex structure. The structure of the, parallel-stranded DNA duplex (PS-duplex) 5'-d(TiGiCAiCiGiGAiCT) +, 5'-d(ACGTGCCTGA), containing the isoguanine (iG) and 5-methyl-isocytosine, (iC) bases, has been determined by NMR refinement. All imino protons, associated with the iG:C, G:iC, and A:T (except the two terminal A:T), basepairs are observed at 2 degrees C, consistent with the formation of a, stable duplex suggested by the earlier Tm measurements [Sugiyama, H., S., Ikeda, and I. Saito. 1996. J. Am. Chem. Soc. 118:9994-9995]. All basepairs, are in the reverse Watson-Crick configuration. The structural, characteristics of the refined PS-duplex are different from those of, B-DNA. The PS duplex has two grooves with similar width (7.0 A) and depth, (7.7 A), in contrast to the two distinct grooves (major groove width 11.7, A, depth 8.5 A, and minor groove width 5.7 A, depth 7.5 A) of B-DNA. The, resonances of the amino protons of iG and C are clearly resolved and, observable, but those of the G and iC are very broad and difficult to, observe. Several intercalators with different complexities, including, ethidium, daunorubicin, and nogalamycin, have been used to probe the, flexibility of the backbone of the (iG, iC)-containing PS-duplex. All of, them produce drug-induced UV/vis spectra identical to their respective, spectra when bound to B-DNA, suggesting that those drugs bind to the (iG, iC)-containing PS-duplex using similar intercalation processes. The, results may be useful in the design of intercalator-conjugated, oligonucleotides for antisense applications. The study presented in this, paper augments our understanding of a growing number of parallel-stranded, DNA structures, including the G-quartet, the i-motif, and the unusual homo, basepaired parallel-stranded double helix. Their possible relevance is, discussed.
About this Structure
1BE5 is a Single protein structure of sequence from [1]. Full crystallographic information is available from OCA.
Reference
Structural studies of a stable parallel-stranded DNA duplex incorporating isoguanine:cytosine and isocytosine:guanine basepairs by nuclear magnetic resonance spectroscopy., Yang XL, Sugiyama H, Ikeda S, Saito I, Wang AH, Biophys J. 1998 Sep;75(3):1163-71. PMID:9726918
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