2ana
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(New page: 200px<br /><applet load="2ana" size="350" color="white" frame="true" align="right" spinBox="true" caption="2ana, resolution 2.500Å" /> '''THE CRYSTAL STRUCTU...)
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THE CRYSTAL STRUCTURE OF D(G-G-G-G-C-C-C-C). A MODEL FOR POLY(DG).POLY(DC)
Overview
The structure of the DNA oligomer d(G-G-G-G-C-C-C-C) has been determined, at a resolution of 2.5 A by single-crystal X-ray methods. There are two, strands in the asymmetric unit, and these coil about each other to form a, right-handed double-helix of the A-type with Watson-Crick hydrogen bonds, between base-pairs. The helix has a shallow minor groove and a deep, water-filled major groove; almost all exposed functional groups on the DNA, are hydrated, and 106 ordered solvent molecules have been found. The two, d(G-G-G-G).d(C-C-C-C) segments in the octamer exhibit similar and uniform, structures, but there is a slight discontinuity at the GpC step between, them. A recurring feature of the structure is the overlap of adjacent, guanine bases in each GpG step, with the five-membered ring of one guanine, stacking on the six-membered ring of its neighbour. There is little or no, overlap between adjacent cytosine rings. Conformational parameters for, these GpG steps are compared with those from other single-crystal X-ray, analyses. In general, GpG steps exhibit high slide, low roll and variable, twist. Models for poly(dG).poly(dC) were generated by applying a simple, rotation and translation to each of the unmodified d(G-G-G-G).d(C-C-C-C), units. Detailed features of these models are shown to be compatible with, various assays of poly(dG).poly(dC) in solution, and are useful in, understanding the polymorphic behaviour of this sequence under a variety, of experimental conditions.
About this Structure
2ANA is a Protein complex structure of sequences from [1]. Full crystallographic information is available from OCA.
Reference
The crystal structure of d(G-G-G-G-C-C-C-C). A model for poly(dG).poly(dC)., McCall M, Brown T, Kennard O, J Mol Biol. 1985 Jun 5;183(3):385-96. PMID:4020865
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