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==STRUCTURE OF A T4 HAIRPIN LOOP ON A Z-DNA STEM AND COMPARISON WITH A-RNA AND B-DNA LOOPS==
<StructureSection load='1d16' size='340' side='right'caption='[[1d16]], [[Resolution|resolution]] 2.10&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1d16]] is a 1 chain structure. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1D16 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1D16 FirstGlance]. <br>
</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=1d16 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1d16 OCA], [https://pdbe.org/1d16 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1d16 RCSB], [https://www.ebi.ac.uk/pdbsum/1d16 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1d16 ProSAT]</span></td></tr>
</table>
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== Publication Abstract from PubMed ==
The synthetic DNA oligomer C-G-C-G-C-G-T-T-T-T-C-G-C-G-C-G crystallizes as a Z-DNA hexamer, capped at one end by a T4 loop. The crystals are monoclinic, space group C2, with a = 57.18 A, b = 21.63 A, c = 36.40 A, beta = 95.22 degrees, and one hairpin molecule per asymmetric unit. The structure of the z-hexamer stem was determined by molecular replacement, and the T4 loop was positioned by difference map methods. The final R factor at 2.1 A resolution for hairpin plus 70 water molecules is 20% for 2 sigma data, with a root-mean-square error of 0.26 A. The (C-G)3 stem resembles the free Z-DNA hexamer with minor crystal packing effects. The T4 loop differs from that observed on a B-DNA stem in solution, or in longer loops in tRNA, in that it shows intraloop and intermolecular interactions rather than base stacking on the final base-pair of the stem. Bases T7, T8 and T9 stack with one another and with the sugar of T7. Two T10 bases from different molecules stack between the C1-G12 terminal base-pairs of a third and fourth molecule, to simulate a T.T "base-pair". Distances between thymine N and O atoms suggest that the two thymine bases are hydrogen bonded, and a keto-enol tautomer pair is favored over disordered keto-keto wobble pairs. The hairpin molecules pack in the crystal in herringbone columns in a manner that accounts well for the observed relative crystal growth rates in a, b and c directions. Hydration seems to be most extensive around the phosphate groups, with lesser hydration within the grooves.

Structure of a T4 hairpin loop on a Z-DNA stem and comparison with A-RNA and B-DNA loops.,Chattopadhyaya R, Grzeskowiak K, Dickerson RE J Mol Biol. 1990 Jan 5;211(1):189-210. PMID:2299669<ref>PMID:2299669</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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== References ==
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</StructureSection>
[[Category: Large Structures]]
[[Category: Chattopadhyaya R]]
[[Category: Dickerson RE]]
[[Category: Grzeskowiak K]]