A sign inversion mechanism for enzymatic supercoiling of DNA

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Science  30 Nov 1979:
Vol. 206, Issue 4422, pp. 1081-1083
DOI: 10.1126/science.227059


Both the introduction and the removal of supertwists by DNA gyrase change the linking number of DNA in steps of two. This surprising finding provides strong evidence that gyrase acts by a mechanism, called sign inversion, whereby a positive supercoil is directly inverted into a negative one via a transient double-strand break.