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Nucleic Acids Res. 2001 Feb 1;29(3):831-40.

Multiple four-stranded conformations of human telomere sequence d(CCCTAA) in solution.

Author information

1
Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan. kanaori@ipc.kit.ac.jp

Abstract

By detailed NMR analysis of a human telomere repeating unit, d(CCCTAA), we have found that three distinct tetramers, each of which consists of four symmetric single-strands, slowly exchange in a slightly acidic solution. Our new finding is a novel i-motif topology (T:-form) where T4 is intercalated between C1 and C2 of the other duplex. The other two tetramers have a topology where C1 is intercalated between C2 and C3 of the other parallel duplex, resulting in the non-stacking T4 residues (R-form), and a topology where C1 is stacked between C3 and T4 of the other duplex (S:-form). From the NMR denaturation profile, the R-form is the most stable of the three structures in the temperature range of 15-50 degrees C, the S:-form the second and the T:-form the least stable. The thermodynamic parameters indicate that the T-form is the most enthalpically driven and entropically opposed, and its population is increased with decreasing temperature. The T-form structure determined by restrained molecular dynamics calculation suggests that inter-strand van der Waals contacts in the narrow grooves should contribute to the enthalpic stabilization of the T-form.

PMID:
11160907
PMCID:
PMC30397
[Indexed for MEDLINE]
Free PMC Article
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