The unusual structure of the human centromere (GGA)2 motif. Unpaired guanosine residues stacked between sheared G.A pairs

J Mol Biol. 1994 Dec 2;244(3):259-68. doi: 10.1006/jmbi.1994.1727.


The centromere of human chromosomes contains multiple repeats of the DNA sequence d(TGGAA)n. This sequence has the interesting property of pairing with itself to form stable duplexes. We have determined the solution structure of the unusual DNA duplex 5'-TGGAATGGAA:TGGAATGGAA-3' at atomic resolution. The duplex contains unpaired staggered guanosine residues, which co-stack by intercalation between sheared G.A and A.G base-pairs to form an interesting new structural motif, the GA-bracketed G-stack. The TGGAA repeat unit contains six "steps", four of which are not Watson-Crick base-pairs.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine / chemistry
  • Base Composition
  • Base Sequence
  • Centromere / chemistry*
  • Centromere / genetics
  • Computer Graphics
  • DNA / chemistry*
  • Guanosine / chemistry
  • Humans
  • Magnetic Resonance Spectroscopy
  • Molecular Sequence Data
  • Nucleic Acid Conformation*
  • Repetitive Sequences, Nucleic Acid*


  • Guanosine
  • DNA
  • Adenosine