1jgr
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(New page: 200px<br /><applet load="1jgr" size="450" color="white" frame="true" align="right" spinBox="true" caption="1jgr, resolution 1.2Å" /> '''Crystal Structure Ana...)
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Revision as of 21:29, 24 November 2007
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Crystal Structure Analysis of the B-DNA Dodecamer CGCGAATTCGCG with Thallium Ions.
Overview
Here we demonstrate that monovalent cations can localize around B-DNA in, geometrically regular, sequence-specific sites in oligonucleotide, crystals. Positions of monovalent ions were determined from, high-resolution X-ray diffraction of DNA crystals grown in the presence of, thallium(I) cations (Tl(+)). Tl(+) has previously been shown to be a, useful K(+) mimic. Tl(+) positions determined by refinement of model to, data are consistent with positions determined using isomorphous F(Tl) -, F(K) difference Fouriers and anomalous difference Fouriers. None of the, observed Tl(+) sites surrounding CGCGAATTCGCG are fully occupied by Tl(+), ions. The most highly occupied sites, located within the G-tract major, groove, have estimated occupancies ranging from 20% to 35%. The, occupancies of the minor groove sites are estimated to be around 10%. The, Tl(+) positions in general are not in direct proximity to phosphate, groups. The A-tract major groove appears devoid of localized cations. The, majority of the observed Tl(+) ions interact with a single duplex and so, are not engaged in lattice interactions or crystal packing. The locations, of the cation sites are dictated by coordination geometry, electronegative, potential, avoidance of electropositive amino groups, and cation-pi, interactions. It appears that partially dehydrated monovalent cations, hydrated divalent cations, and polyamines compete for a common binding, region on the floor of the G-tract major groove.
About this Structure
1JGR is a Protein complex structure of sequences from [1] with MG and TL as ligands. Full crystallographic information is available from OCA.
Reference
Locating monovalent cations in the grooves of B-DNA., Howerton SB, Sines CC, VanDerveer D, Williams LD, Biochemistry. 2001 Aug 28;40(34):10023-31. PMID:11513580
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