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Native supercoiling of DNA: The effects of DNA gyrase and ω protein in E. coli

✍ Scribed by Mirkin, S. M. ;Zaitsev, E. N. ;Panyutin, I. G. ;Lyamichev, V. I.

Publisher
Springer
Year
1984
Tongue
English
Weight
557 KB
Volume
196
Category
Article
ISSN
0026-8925

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✦ Synopsis

This study deals with the effects of a temperature-sensitive (ts) mutation at the gene encoding the DNA gyrase B subunit (gyrBts) and a deletion of the top gene encoding the omega protein upon the superhelical density of the pAO3 plasmid in E. coli cells. The alteration of the DNA gyrase B subunit is shown to lead to a partial relaxation of DNA. On the other hand, the lack of omega protein due to the top gene deletion leads to an abnormally high degree of DNA supercoiling. In a double gyrBts delta top mutant the DNA supercoiling is greater than native at the permissive temperature, while under nonpermissive conditions a partial relaxation is observed. However, the pattern of DNA relaxation in the latter case is quite different from that in a single gyrBts mutant. The conclusion is that the native supercoiling of DNA in the cell is maintained through the counter-activities of DNA gyrase and the omega protein.

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