title: Altered topoisomerase activities may be involved in the regulation of DNA supercoiling in aerobic-anaerobic transitions in Escherichia coli.
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.
authors.affiliation: Dept. de Bioquímica de la Nutrición, Conicet-Universidad Nacional de Tucumán, Argentina.
authors.forename: S
authors.initials: S
authors.lastname: Cortassa
authors.forename: M A
authors.initials: MA
authors.lastname: Aon
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000332:Aerobiosis / Q000235:genetics*; D000693:Anaerobiosis / Q000235:genetics*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism*; D004278:DNA, Superhelical / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D007700:Kinetics
chemical_list: D004269:DNA, Bacterial; D004278:DNA, Superhelical; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II