DNA A-tracts are not curved in solutions containing high concentrations of monovalent cations.
Biochemistry
; 52(24): 4138-48, 2013 Jun 18.
Article
en En
| MEDLINE
| ID: mdl-23675817
ABSTRACT
The intrinsic curvature of seven 98 bp DNA molecules containing up to four centrally located A6-tracts has been measured by gel and capillary electrophoresis as a function of the number and arrangement of the A-tracts. At low cation concentrations, the electrophoretic mobility observed in polyacrylamide gels and in free solution decreases progressively with the increasing number of phased A-tracts, as expected for DNA molecules with increasingly curved backbone structures. Anomalously slow electrophoretic mobilities are also observed for DNA molecules containing two pairs of phased A-tracts that are out of phase with each other, suggesting that out-of-phase distortions of the helix backbone do not cancel each other out. The mobility decreases observed for the A-tract samples are due to curvature, not cation binding in the A-tract minor groove, because identical free solution mobilities are observed for a molecule with four out-of-phase A-tracts and one with no A-tracts. Surprisingly, the curvature of DNA A-tracts is gradually lost when the monovalent cation concentration is increased to â¼200 mM, regardless of whether the cation is a hydrophilic ion like Na+, NH4+, or Tris+ or a hydrophobic ion like tetrabutylammonium. The decrease in A-tract curvature with increasing ionic strength, along with the known decrease in A-tract curvature with increasing temperature, suggests that DNA A-tracts are not significantly curved under physiological conditions.
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
ADN
/
Cationes Monovalentes
Idioma:
En
Revista:
Biochemistry
Año:
2013
Tipo del documento:
Article
País de afiliación:
Estados Unidos