Multiple four-stranded conformations of human telomere sequence d(CCCTAA) in solution.
Nucleic Acids Res
; 29(3): 831-40, 2001 Feb 01.
Article
em En
| MEDLINE
| ID: mdl-11160907
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.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
DNA
/
Telômero
/
Conformação de Ácido Nucleico
Limite:
Humans
Idioma:
En
Ano de publicação:
2001
Tipo de documento:
Article