Structure of poly d(AI)·poly d(CT) in two different packing arrangements

Rengaswami Chandrasekaran, Akella Radha, Hye Shin Park

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

X-ray diffraction analysis of poly d(AI)·poly d(CT) in oriented and polycrystalline fibers has revealed the DNA structure to be a 10-fold, right-handed, antiparallel, Watson-Crick base paired double helix in two distinct packing arrangements corresponding to one and two helices, respectively, in the unit cell. The helix pitch is 32.1 Å and 32.4 Å in the two cases, almost 1.5 Å shorter than in classical B-DNA. The resulting B'-DNA geometry, described in terms of a tetranucleotide repeat which is conformationally similar to B-DNA, has its minor groove closely shut and major groove correspondingly widened, thus striking a sharp morphological contrast to B-DNA. According to difference electron density maps, a spine of hydration along the minor groove connects both strands and provides structural stability; ordered sodium ions and water molecules are actively involved in bridging the phosphate groups of neighboring helices. The crystallographic R-values for these two allomorphs are 0.26 and 0.20, respectively, for data up to 3.0 Å resolution.

Original languageEnglish (US)
Pages (from-to)285-305
Number of pages21
JournalJournal of Biomolecular Structure and Dynamics
Volume15
Issue number2
Publication statusPublished - 1997

    Fingerprint

ASJC Scopus subject areas

  • Molecular Biology
  • Structural Biology

Cite this