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  • Title: Altered topoisomerase activities may be involved in the regulation of DNA supercoiling in aerobic-anaerobic transitions in Escherichia coli.
    Author: Cortassa S, Aon MA.
    Journal: Mol Cell Biochem; 1993 Sep 22; 126(2):115-24. PubMed ID: 8302289.
    Abstract:
    This study uncovers a new mechanism of regulation of DNA supercoiling operative in vivo upon an aerobic-anaerobic transition in Escherichia coli. Exponentially growing aerobic batch cultures were subjected to a shift to anaerobic conditions. The ratio [ATP]/[ADP] remained essentially constant at 8.5 in the aerobic culture and after a transition to anaerobiosis while DNA supercoiling increased noticeably upon anaerobiosis. This result indicated that the mechanism of regulation of DNA supercoiling by the [ATP]/[ADP] ratio was not operative. The increase in DNA supercoiling was followed by a large decrease in the DNA-relaxing activity of topoisomerase I while gyrase activity remained relatively constant. This decrease in the activity of topoisomerase I is likely to be responsible for the increase in DNA supercoiling.
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