2dnd
From Proteopedia
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A BIFURCATED HYDROGEN-BONDED CONFORMATION IN THE D(A.T) BASE PAIRS OF THE DNA DODECAMER D(CGCAAATTTGCG) AND ITS COMPLEX WITH DISTAMYCIN
Overview
The crystal structures of d(CGCA3T3GCG) complex to the antitumor drug, distamycin and the DNA fragment alone were solved by x-ray diffraction at, 2.2 and 2.5 A resolution, respectively. The drug lies in the narrow minor, groove near the center of the B-DNA fragment covering 5 of the 6 A.T base, pairs. It is bound to the DNA by hydrogen bonding, van der Waals, and, electrostatic interactions. In addition, the DNA was found to have an, unusual conformation in the (dA)3.(dT)3 regions. These base pairs have a, high positive propeller twist so that in the major groove the adenine, amino group is located intermediate between the carbonyl O-4 groups of two, adjacent thymines of the opposite strand, making bifurcated hydrogen bonds, to the two thymine residues. This suggests a model to explain the unusual, properties of poly-(dA).poly(dT) in which a modified B conformation is, associated with a large propeller twist of the bases and a set of, continuous bifurcating hydrogen bonds along the major groove, which may, provide incremental stability to these segments. In addition, shorter, segments of (dA)3-6.(dT)3-6 may have this conformation in the midst of, B-DNA and stabilize bends in the DNA that may be associated with stacking, on one of the high propeller-twisted bases at the ends of these segments.
About this Structure
2DND is a Protein complex structure of sequences from [1] with as ligand. Full crystallographic information is available from OCA.
Reference
A bifurcated hydrogen-bonded conformation in the d(A.T) base pairs of the DNA dodecamer d(CGCAAATTTGCG) and its complex with distamycin., Coll M, Frederick CA, Wang AH, Rich A, Proc Natl Acad Sci U S A. 1987 Dec;84(23):8385-9. PMID:3479798
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