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1p0u
From Proteopedia
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Sheared G/C Base Pair
Overview
Stable DNA loop structures closed by a novel G.C base-pair have been determined for the single-residue d(GXC) loops (X=A, T, G or C) in low-salt solution by high-resolution nuclear magnetic resonance (NMR) techniques. The closing G.C base-pair in these loops is not of the canonical Watson-Crick type, but adopts instead a unique sheared-type (trans Watson-Crick/sugar-edge) pairing, like those occurring in the sheared mismatched G.A or A.C base-pair, to draw the two opposite strands together. The cytidine residue in the closing base-pair is transformed into the rare syn domain to form two H-bonds with the guanine base and to prevent the steric clash between the G 2NH(2) and the C H-5 protons. Besides, the sugar pucker of the syn cytidine is still located in the regular C2'-endo domain, unlike the C3'-endo domain adopted for the pyrimidines of the out-of-alternation left-handed Z-DNA structure. The facile formation of the compact d(GXC) loops closed by a unique sheared-type G(anti).C(syn) base-pair demonstrates the great potential of the single-stranded d(GXC) triplet repeats to fold into stable hairpins.
About this Structure
1P0U is a Protein complex structure of sequences from [1]. Full crystallographic information is available from OCA.
Reference
Sheared-type G(anti).C(syn) base-pair: a unique d(GXC) loop closure motif., Chin KH, Chou SH, J Mol Biol. 2003 May 30;329(2):351-61. PMID:12758081
Page seeded by OCA on Thu Mar 20 13:18:14 2008
