2hk4
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(New page: 200px<br /><applet load="2hk4" size="350" color="white" frame="true" align="right" spinBox="true" caption="2hk4" /> '''Dimeric solution structure of the cyclic oct...)
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Revision as of 18:22, 29 January 2008
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Dimeric solution structure of the cyclic octamer d(CCGTCCGT)
Overview
Four-stranded nucleic acid structures are central to many processes in, biology and in supramolecular chemistry. It has been shown recently that, four-stranded DNA structures are not only limited to the classical guanine, quadruplex but also can be formed by tetrads resulting from the, association of Watson-Crick base pairs. Such an association may occur, through the minor or the major groove side of the base pairs. Structures, stabilized by minor groove tetrads present distinctive features, clearly, different from the canonical guanine quadruplex, making these quadruplexes, a unique structural motif. Within our efforts to study the sequence, requirements for the formation of this unusual DNA motif, we have, determined the solution structure of the cyclic oligonucleotide dpCCGTCCGT, by two-dimensional NMR spectroscopy and restrained molecular dynamics., This molecule self-associates, forming a symmetric dimer stabilized by two, G:C:G:C tetrads with intermolecular G-C base pairs. Interestingly, although the overall three-dimensional structure is similar to that found, in other cyclic and linear oligonucleotides of related sequences, the, tetrads that stabilize the structure of dpCCGTCCGT are different to other, minor groove G:C:G:C tetrads found earlier. Whereas in previous cases the, G-C base pairs aligned directly, in this new tetrad the relative position, of the two base pairs is slipped along the axis defined by the base pairs., This is the first time that a quadruplex structure entirely stabilized by, slipped minor groove G:C:G:C tetrads is observed in solution or in the, solid state. However, an analogous arrangement of G-C base pairs occurs, between the terminal residues of contiguous duplexes in some DNA crystals., This structural polymorphism between minor groove GC tetrads may be, important in stabilization of higher order DNA structures.
About this Structure
2HK4 is a Protein complex structure of sequences from [1]. Full crystallographic information is available from OCA.
Reference
Four-stranded DNA structures can be stabilized by two different types of minor groove G:C:G:C tetrads., Escaja N, Gomez-Pinto I, Pedroso E, Gonzalez C, J Am Chem Soc. 2007 Feb 21;129(7):2004-14. Epub 2007 Jan 30. PMID:17260988
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