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Molecular mechanics calculations on a triple stranded DNA involving C+.G-T and T.A+-C mismatched base triples.

Authors
  • Bhaumik, S R
  • Chary, K V
  • Govil, G
Type
Published Article
Journal
Journal of biomolecular structure & dynamics
Publication Date
Dec 01, 1998
Volume
16
Issue
3
Pages
527–534
Identifiers
PMID: 10052611
Source
Medline
License
Unknown

Abstract

We have carried out molecular modeling of a triple stranded pyrimidine(Y). purine(R): pyrimidine(Y) (where ':' refers to Watson-Crick and '.' to Hoogsteen bonding) DNA, formed by a homopurine (d-TGAGGAAAGAAGGT) and homo-pyrimidine (d-CTCCTTTCTTCC). Molecular mechanics calculations using NMR constraints have provided a detailed three dimensional structure of the triplex. The entire stretches of purine and the pyrimidine nucleotides have a conformation close to B-DNA. The three strands are held by the canonical C+.G:C and T.A:T hydrogen bonds. The structure also contains two mismatch C+.G-T and T.A+-C base triples which have been characterized for the first time. In the A+-C base-pair of the T.A+-C triple, both hydrogen donors are situated on the purine (A+(1N) and A+(6N)). We observe a unique hydrogen bonding interaction scheme in case of C+.G-T where one acceptor, G(60), is bonded to three donors (C+(3NH), C+(4NH2) and T(3NH)). Though the C+.G-T base triple is less stable than C+.G:C, it is significantly more stable than T.A:T. On the other hand, T.A+-C is as stable as the T.A:T base triad.

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