Winding of the DNA helix by divalent metal ions | Zendy

Y. Xu | Zendy

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Winding of the DNA helix by divalent metal ions

Author(s) -

Y. Xu

Publication year - 1997

Publication title -

nucleic acids research

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 9.008

H-Index - 537

eISSN - 1362-4954

pISSN - 0305-1048

DOI - 10.1093/nar/25.20.4067

Subject(s) - dna supercoil , divalent , dna , biology , helix (gastropod) , agarose , molecule , agarose gel electrophoresis , biophysics , crystallography , biochemistry , chemistry , dna replication , ecology , organic chemistry , snail

When supercoiled pBR322 DNA was relaxed at 0 or 22 degrees C by topoisomerase I in the presence of the divalent cations Ca2+, Mn2+ or Co2+, the resulting distributions of topoisomers observed at 22 degrees C had positive supercoils, up to an average delta Lk value of +8.6 (for Ca2+at 0 degrees C), corresponding to an overwinding of the helix by 0.7 degrees/bp. An increase of the divalent cation concentration in the reaction mixture above 50 mM completely reversed the effect. When such ions were present in agarose electrophoresis gels, they caused a relaxation of positively supercoiled DNA molecules, and thus allowed a separation of strongly positively supercoiled topoisomers. The effect of divalent cations on DNA adds a useful tool for the study of DNA topoisomers, for the generation as well as separation of positively supercoiled DNA molecules.

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