A bifurcated hydrogen-bonded conformation in the d(A.T) base pairs of the DNA dodecamer d(CGCAAATTTGCG) and its complex with distamycin.

M. Coll, C. A. Frederick, A. H. Wang, A. Rich

Research output: Contribution to journalArticlepeer-review

731 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)8385-8389
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume84
Issue number23
DOIs
Publication statusPublished - Dec 1987
Externally publishedYes

ASJC Scopus subject areas

  • General

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