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

Citation
K. Kanaori et al., Multiple four-stranded conformations of human telomere sequence d(CCCTAA) in solution, NUCL ACID R, 29(3), 2001, pp. 831-840
Citations number
36
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
NUCLEIC ACIDS RESEARCH
ISSN journal
0305-1048 → ACNP
Volume
29
Issue
3
Year of publication
2001
Pages
831 - 840
Database
ISI
SICI code
0305-1048(20010201)29:3<831:MFCOHT>2.0.ZU;2-9
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 sy mmetric single-strands, slowly exchange in a slightly acidic solution. Our new finding is a novel i-motif topology (T-form) where T4 is intercalated b etween C1 and C2 of the other duplex. The other two tetramers have a topolo gy 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 C 1 is stacked between C3 and T4 of the other duplex (S-form). From the NMR d enaturation profile, the R-form is the most stable of the three structures in the temperature range of 15-50 degreesC, the S-form the second and the T -form the least stable. The thermodynamic parameters indicate that the T-fo rm is the most enthalpically driven and entropically opposed, and its popul ation is increased with decreasing temperature. The T-form structure determ ined by restrained molecular dynamics calculation suggests that inter-stran d van der Waals contacts in the narrow grooves should contribute to the ent halpic stabilization of the T-form.