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Internal Sodium Ions and Water Molecules in Guanine Quadruplexes: Magnetic Relaxation Dispersion Studies of [d(G3T4G3)]2 and [d(G4T4G4)]2

Snoussi, Karim LU and Halle, Bertil LU (2008) In Biochemistry 47(46). p.12219-12229
Abstract
The structural stability of guanine quadruplexes depends critically on an unusual configuration of dehydrated Na+ or K+ ions, closely spaced along the central axis of the quadruplex. Crystallography and NMR spectroscopy indicate that these internal ions can be located between the G-quartet planes as well as in the thymine loops, but the precise ion coordination has been firmly established in only a few cases. Here, we examine the bimolecular diagonal-looped foldback quadruplexes [d(G3T4G3)]2 (Q3) and [d(G4T4G4)]2 (Q4) by 2H, 17O, and 23Na magnetic relaxation dispersion (MRD). The MRD data indicate that both quadruplexes contain Na+ ions between the T4 loops and the terminal G-quartets and that these ions have one water ligand. These ions... (More)
The structural stability of guanine quadruplexes depends critically on an unusual configuration of dehydrated Na+ or K+ ions, closely spaced along the central axis of the quadruplex. Crystallography and NMR spectroscopy indicate that these internal ions can be located between the G-quartet planes as well as in the thymine loops, but the precise ion coordination has been firmly established in only a few cases. Here, we examine the bimolecular diagonal-looped foldback quadruplexes [d(G3T4G3)]2 (Q3) and [d(G4T4G4)]2 (Q4) by 2H, 17O, and 23Na magnetic relaxation dispersion (MRD). The MRD data indicate that both quadruplexes contain Na+ ions between the T4 loops and the terminal G-quartets and that these ions have one water ligand. These ions exchange with external ions on a time scale of 10−60 μs at 27 °C, while their highly ordered water ligands have residence times in the range 10−8−10−6 s. The MRD data indicate that Q4 contains three Na+ ions in the stem sites, in agreement with previous solid-state 23Na NMR findings but contrary to the only crystal structure of this quadruplex. For Q3, the MRD data suggest a less symmetric coordination of the two stem ions. In both quadruplexes, the stem ions have residence times of 0.6−1.0 ms at 27 °C. The equilibrium constant for Na+ → K+ exchange is ∼4 for both loop and stem sites in Q3, in agreement with previous 1H NMR findings. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Biochemistry
volume
47
issue
46
pages
12219 - 12229
publisher
The American Chemical Society
external identifiers
  • wos:000260790600031
  • scopus:56249115189
ISSN
0006-2960
DOI
10.1021/bi801657s
language
English
LU publication?
yes
id
8f8b0d10-beda-44f5-80f1-b6bc622a8c31 (old id 1270164)
alternative location
http://dx.doi.org/10.1021/bi801657s
date added to LUP
2008-12-01 11:46:51
date last changed
2017-07-30 03:32:13
@article{8f8b0d10-beda-44f5-80f1-b6bc622a8c31,
  abstract     = {The structural stability of guanine quadruplexes depends critically on an unusual configuration of dehydrated Na+ or K+ ions, closely spaced along the central axis of the quadruplex. Crystallography and NMR spectroscopy indicate that these internal ions can be located between the G-quartet planes as well as in the thymine loops, but the precise ion coordination has been firmly established in only a few cases. Here, we examine the bimolecular diagonal-looped foldback quadruplexes [d(G3T4G3)]2 (Q3) and [d(G4T4G4)]2 (Q4) by 2H, 17O, and 23Na magnetic relaxation dispersion (MRD). The MRD data indicate that both quadruplexes contain Na+ ions between the T4 loops and the terminal G-quartets and that these ions have one water ligand. These ions exchange with external ions on a time scale of 10−60 μs at 27 °C, while their highly ordered water ligands have residence times in the range 10−8−10−6 s. The MRD data indicate that Q4 contains three Na+ ions in the stem sites, in agreement with previous solid-state 23Na NMR findings but contrary to the only crystal structure of this quadruplex. For Q3, the MRD data suggest a less symmetric coordination of the two stem ions. In both quadruplexes, the stem ions have residence times of 0.6−1.0 ms at 27 °C. The equilibrium constant for Na+ → K+ exchange is ∼4 for both loop and stem sites in Q3, in agreement with previous 1H NMR findings.},
  author       = {Snoussi, Karim and Halle, Bertil},
  issn         = {0006-2960},
  language     = {eng},
  number       = {46},
  pages        = {12219--12229},
  publisher    = {The American Chemical Society},
  series       = {Biochemistry},
  title        = {Internal Sodium Ions and Water Molecules in Guanine Quadruplexes: Magnetic Relaxation Dispersion Studies of [d(G3T4G3)]2 and [d(G4T4G4)]2},
  url          = {http://dx.doi.org/10.1021/bi801657s},
  volume       = {47},
  year         = {2008},
}