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PDBsum entry 1d77
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References listed in PDB file
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Key reference
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Title
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Crystal structure of a b-Dna dodecamer containing inosine, D(cgciaattcgcg), At 2.4 a resolution and its comparison with other b-Dna dodecamers.
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Authors
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J.C.Xuan,
I.T.Weber.
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Ref.
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Nucleic Acids Res, 1992,
20,
5457-5464.
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PubMed id
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Abstract
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The crystal structure of the dodecamer, d(CGCIAATTCGCG), has been determined at
2.4 A resolution by molecular replacement, and refined to an R-factor of 0.174.
The structure is isomorphous with that of the B-DNA dodecamer, d(CGCGAATTCGCG),
in space group P2(1)2(1)2(1) with cell dimensions of a = 24.9, b = 40.4, and c =
66.4 A. The initial difference Fourier maps clearly indicated the presence of
inosine instead of guanine. The structure was refined with 44 water molecules,
and compared to the parent dodecamer. Overall the two structures are very
similar, and the I:C forms Watson-Crick base pairs with similar hydrogen bond
geometry to the G:C base pairs. The propeller twist angle is low for I4:C21 and
relatively high for the I16:C9 base pair (-3.2 degrees compared to -23.0
degrees), and the buckle angles alter, probably due to differences in the
contacts with symmetry related molecules in the crystal lattice. The central
base pairs of d(CGCIAATTCGCG) show the large propeller twist angles, and the
narrow minor groove that characterize A-tract DNA, although I:C base pairs
cannot form the major groove bifurcated hydrogen bonds that are possible for A:T
base pairs.
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Headers
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