223d

<StructureSection load='223d' size='340' side='right' caption='[[223d]], [[Resolution|resolution]] 1.70&Aring;' scene=''>

<table><tr><td colspan='2'>[[223d]] is a 2 chain structure. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=223D OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=223D FirstGlance]. <br>

</td></tr><tr id='NonStdRes'><td class="sblockLbl"><b>[[Non-Standard_Residue|NonStd Res:]]</b></td><td class="sblockDat"><scene name='pdbligand=C46:6H,8H-3,4-DIHYDROPYRIMIDO[4,5-C][1,2]OXAZIN-7-0NE(CYTIDINE)-5-MONOPHOSPHATE'>C46</scene></td></tr>

<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=223d FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=223d OCA], [http://pdbe.org/223d PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=223d RCSB], [http://www.ebi.ac.uk/pdbsum/223d PDBsum]</span></td></tr>

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== Publication Abstract from PubMed ==

The pyrimidine nucleobase analogue 6H,8H-3,4-dihydropyrimido[4,5-c]- [1,2]oxazin-7-one (P) is a mimic both of cytosine and thymine, since it can form stable hydrogen-bonded base-pairs with either guanine or adenine. To investigate the geometric properties of pairing with guanine in a DNA double helix, the structure of d(CGCGPG)2 has been determined by single crystal X-ray analysis. The oligonucleotide crystallised as a left-handed Z-DNA duplex in the orthorhombic space group P2(1)2(1)2(1) with cell dimensions a = 18.23 A, b = 30.63 A, c = 43.78 A. Refinement using NUCLSQ with 51 water molecules included in the final model converged at R = 0.179 (Rw = 0.159) for 2798 reflections (F &gt; 2 sigma (F)) in the range 8 A to 1.7 A. Remarkably, the two P.G pairs in the hexamer duplex are different: Watson-Crick and wobble types separately illustrate both cytosine-like and thymine-like behaviour. The result suggests that mutagenesis experiments involving P and other analogues which display pronounced base-pairing ambivalence can be used to examine the structural basis of substrate discrimination by polymerases that is essential to accurate genetic replication.

Direct observation of two base-pairing modes of a cytosine-thymine analogue with guanine in a DNA Z-form duplex: significance for base analogue mutagenesis.,Moore MH, Van Meervelt L, Salisbury SA, Lin PK, Brown DM J Mol Biol. 1995 Sep 1;251(5):665-73. PMID:7666418<ref>PMID:7666418</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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<div class="pdbe-citations 223d" style="background-color:#fffaf0;"></div>

== References ==

<references/>

[[Category: Brown, D M]]

[[Category: Lin, P Kong Thoo]]

[[Category: Meervelt, L Van]]

[[Category: Moore, M H]]

[[Category: Salisbury, S A]]

[[Category: Dna]]

[[Category: Z-dna]]