5'-CGA Sequence is a strong motif for homo base-paired parallel-stranded DNA duplex as revealed by NMR analysis

H. Robinson, A. H.J. Wang

Research output: Contribution to journalArticlepeer-review

59 Citations (Scopus)

Abstract

The structure of the non-self-complementary DNA heptamer d(CGACGAC) at low pH has been determined by the quantitative NMR refinement procedure designated SPEDREF (SPEctral-Driven REFinement). Acid-base titration of the molecule indicated a prominent n = 2 pK(a) near 6.8. In the pH range up to 6.0, the heptamer forms a remarkably stable double helix, which was conclusively shown to be an unusual homobase-paired parallel-stranded double helix (termed II-DNA). In this II-DNA helix, the 5'-CGA trinucleotide is the structural motif that accounts for the stability, with the C+C hemiprotonated base pair (in which C+ is N3-protonated cytosine) providing for the alignment site and the unusual interstrand G-A base stack in the GpA step furnishing the additional stabilizing forces. The exchangeable proton data from two-dimensional nuclear Overhauser effect spectroscopy are in total agreement with the refined structure. We conclude that the 5'-CGA or other related sequences (e.g., 5'-CCGA) are powerful motifs in promoting the II- DNA or II-RNA conformations that may play certain biological functions.

Original languageEnglish
Pages (from-to)5224-5228
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume90
Issue number11
DOIs
Publication statusPublished - 1993
Externally publishedYes

Keywords

  • non-Watson-Crick base pairing
  • repetitive sequence
  • structural refinement
  • unusual DNA conformation

ASJC Scopus subject areas

  • General

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