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New page: left|200px<br /><applet load="1xa2" size="450" color="white" frame="true" align="right" spinBox="true" caption="1xa2, resolution 1.71Å" /> '''Cobalt hexammine ind...
 
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[[Image:1xa2.gif|left|200px]]<br /><applet load="1xa2" size="450" color="white" frame="true" align="right" spinBox="true"
caption="1xa2, resolution 1.71&Aring;" />
'''Cobalt hexammine induced tautomeric shift in Z-DNA: the structure of d(CGCGCA).d(TGCGCG) in two crystal forms'''<br />


==Overview==
==Cobalt hexammine induced tautomeric shift in Z-DNA: the structure of d(CGCGCA).d(TGCGCG) in two crystal forms==
We report here the crystal structure of the DNA hexamer duplex, d(CGCGCA)*d(TGCGCG) at 1.71 A resolution. The crystals, in orthorhombic, space group, were grown in the presence of cobalt hexammine, a known, inducer of the left-handed Z form of DNA. The interaction of this ion with, the DNA helix results in a change of the adenine base from the common, amino tautomeric form to the imino tautomer. Consequently the A:T base, pair is disrupted from the normal Watson-Crick base pairing to a 'wobble', like base pairing. This change is accommodated easily within the helix, and the helical parameters are those expected for Z-DNA. When the cobalt, hexammine concentration is decreased slightly in the crystallization, conditions, the duplex crystallizes in a different, hexagonal space group, with two hexamer duplexes in the asymmetric unit. One of these is situated, on a crystallographic 6-fold screw axis, leading to disorder. The, tautomeric shift is not observed in this space group. We show that the, change in inter-helix interactions that lead to the two different space, groups probably arise from the small decrease in ion concentration, and, consequently disordered positions for the ion.
<StructureSection load='1xa2' size='340' side='right'caption='[[1xa2]], [[Resolution|resolution]] 1.71&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1xa2]] is a 2 chain structure. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1XA2 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1XA2 FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.71&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=NCO:COBALT+HEXAMMINE(III)'>NCO</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1xa2 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1xa2 OCA], [https://pdbe.org/1xa2 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1xa2 RCSB], [https://www.ebi.ac.uk/pdbsum/1xa2 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1xa2 ProSAT]</span></td></tr>
</table>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
We report here the crystal structure of the DNA hexamer duplex d(CGCGCA)*d(TGCGCG) at 1.71 A resolution. The crystals, in orthorhombic space group, were grown in the presence of cobalt hexammine, a known inducer of the left-handed Z form of DNA. The interaction of this ion with the DNA helix results in a change of the adenine base from the common amino tautomeric form to the imino tautomer. Consequently the A:T base pair is disrupted from the normal Watson-Crick base pairing to a 'wobble' like base pairing. This change is accommodated easily within the helix, and the helical parameters are those expected for Z-DNA. When the cobalt hexammine concentration is decreased slightly in the crystallization conditions, the duplex crystallizes in a different, hexagonal space group, with two hexamer duplexes in the asymmetric unit. One of these is situated on a crystallographic 6-fold screw axis, leading to disorder. The tautomeric shift is not observed in this space group. We show that the change in inter-helix interactions that lead to the two different space groups probably arise from the small decrease in ion concentration, and consequently disordered positions for the ion.


==About this Structure==
Cobalt hexammine induced tautomeric shift in Z-DNA: the structure of d(CGCGCA)*d(TGCGCG) in two crystal forms.,Thiyagarajan S, Rajan SS, Gautham N Nucleic Acids Res. 2004 Nov 8;32(19):5945-53. Print 2004. PMID:15534365<ref>PMID:15534365</ref>
1XA2 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/ ] with NCO as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1XA2 OCA].


==Reference==
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
Cobalt hexammine induced tautomeric shift in Z-DNA: the structure of d(CGCGCA)*d(TGCGCG) in two crystal forms., Thiyagarajan S, Rajan SS, Gautham N, Nucleic Acids Res. 2004 Nov 8;32(19):5945-53. Print 2004. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=15534365 15534365]
</div>
[[Category: Protein complex]]
<div class="pdbe-citations 1xa2" style="background-color:#fffaf0;"></div>
[[Category: Gautham, N.]]
== References ==
[[Category: Rajan, S.S.]]
<references/>
[[Category: Thiyagarajan, S.]]
__TOC__
[[Category: NCO]]
</StructureSection>
[[Category: double helix]]
[[Category: Large Structures]]
[[Category: z-dna]]
[[Category: Gautham N]]
 
[[Category: Rajan SS]]
''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Sun Nov 25 01:44:40 2007''
[[Category: Thiyagarajan S]]
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