284d

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spinqualitylabelsall models 284d, resolution 1.100Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

THE BI-LOOP, A NEW GENERAL FOUR-STRANDED DNA MOTIF

Overview

The crystal structure of the cyclic octanucleotide d<pATTCATTC> contains, two independent molecules that form a novel quadruplex by means of, intermolecular Watson-Crick A.T pairs and base stacking. A virtually, identical quadruplex composed of G.C pairs was found by earlier x-ray, analysis of the linear heptamer d(GCATGCT), when the DNA was looped in the, crystal. The close correspondence between these two structures of markedly, dissimilar oligonucleotides suggests that they are both examples of a, previously unrecognized motif. Their nucleotide sequences have little in, common except for two separated 5'-purine-pyrimidine dinucleotides forming, the quadruplex, and by implication these so-called "bi-loops" could occur, widely in natural DNA. Such structures provide a mechanism for noncovalent, linking of polynucleotides in vivo. Their capacity to associate by base, stacking, demonstrated in the crystal structure of d(GCATGCT), creates a, compact molecular framework made up of four DNA chains within which strand, exchange could take place.

About this Structure

284D is a Protein complex structure of sequences from [1] with and as ligands. Full crystallographic information is available from OCA.

Reference

The bi-loop, a new general four-stranded DNA motif., Salisbury SA, Wilson SE, Powell HR, Kennard O, Lubini P, Sheldrick GM, Escaja N, Alazzouzi E, Grandas A, Pedroso E, Proc Natl Acad Sci U S A. 1997 May 27;94(11):5515-8. PMID:9159103

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