The twist, writhe and overall shape of supercoiled DNA change during counterion-induced transition from a loosely to a tightly interwound superhelix. Possible implications for DNA structure in vivo.

Details

Serval ID
serval:BIB_0BE59B59E0A3
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
The twist, writhe and overall shape of supercoiled DNA change during counterion-induced transition from a loosely to a tightly interwound superhelix. Possible implications for DNA structure in vivo.
Journal
Journal of Molecular Biology
Author(s)
Bednar J., Furrer P., Stasiak A., Dubochet J., Egelman E.H., Bates A.D.
ISSN
0022-2836[print], 0022-2836[linking]
Publication state
Published
Issued date
01/1994
Volume
235
Number
3
Pages
825-847
Language
english
Notes
Publication types: Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S. ; Research Support, U.S. Gov't, P.H.S.
Publication Status: ppublish
Abstract
A cryo-electron microscopy study of supercoiled DNA molecules freely suspended in cryo-vitrified buffer was combined with Monte Carlo simulations and gel electrophoretic analysis to investigate the role of intersegmental electrostatic repulsion in determining the shape of supercoiled DNA molecules. It is demonstrated here that a decrease of DNA-DNA repulsion by increasing concentrations of counterions causes a higher fraction of the linking number deficit to be partitioned into writhe. When counterions reach concentrations likely to be present under in vivo conditions, naturally supercoiled plasmids adopt a tightly interwound conformation. In these tightly supercoiled DNA molecules the opposing segments of interwound superhelix seem to directly contact each other. This form of supercoiling, where two DNA helices interact laterally, may represent an important functional state of DNA. In the particular case of supercoiled minicircles (178 bp) the delta Lk = -2 topoisomers undergo a sharp structural transition from almost planar circles in low salt buffers to strongly writhed "figure-eight" conformations in buffers containing neutralizing concentrations of counterions. Possible implications of this observed structural transition in DNA are discussed.
Keywords
DNA, Superhelical/chemistry, DNA, Superhelical/ultrastructure, Electrophoresis, Agar Gel, Escherichia coli, Magnesium/chemistry, Microscopy, Electron, Molecular Weight, Monte Carlo Method, Nucleic Acid Conformation, Plasmids, Sodium Chloride/chemistry, Thermodynamics
Pubmed
Web of science
Create date
24/01/2008 10:25
Last modification date
20/08/2019 12:33
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