223d

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

spinqualitylabelsall models 223d, resolution 1.70Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 223d is a 2 chain structure. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. NonStd Res: C46 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT 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 > 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 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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