Reverse gyrases are topoisomerases that introduce positive supercoils into DNA in an ATP-dependent reaction. They consist of a helicase domain and a topoisomerase domain that closely cooperate in catalysis. The mechanism of the functional cooperation of these domains has remained elusive. Recent studies have shown that the helicase domain is a nucleotide-regulated conformational switch that alt...

We have cloned Staphylococcus aureus DNA gyrase and topoisomerase IV and expressed them in Escherichia coli as polyhistidine-tagged proteins to facilitate purification and eliminate contamination by host enzymes. The enzyme preparations had specific activities similar to previously reported values. Potassium glutamate (K-Glu) stimulated the drug-induced DNA cleavage activity and was optimal bet...

DNA topoisomerases manage chromosome supercoiling and organization in all forms of life. Gyrase, a prokaryotic heterotetrameric type IIA topo, introduces negative supercoils into DNA by an ATP-dependent strand passage mechanism. All gyrase orthologs rely on a homologous set of catalytic domains for function; however, these enzymes also can possess species-specific auxiliary regions. The gyrases...

Reverse gyrase is an ATP-dependent topoisomerase that is unique to hyperthermophilic archaea and eubacteria. The only reverse gyrase structure determined to date has revealed the arrangement of the N-terminal helicase domain and the C-terminal topoisomerase domain that intimately cooperate to generate the unique function of positive DNA supercoiling. Although the structure has elicited hypothes...

BACKGROUND The topological state of DNA is a result of the diverse influences of various topoisomerases present in the cell. Amongst these, DNA gyrase is the only enzyme that is capable of supercoiling DNA. In all the eubacterial cells tested so far, DNA gyrase has proved to be essential for survival. We have earlier cloned gyr genes from Mycobacterium smegmatis. Unlike the situation in Escheri...

Plasmid topology varies transiently in hyperthermophilic archaea during thermal stress. As in mesophilic bacteria, DNA linking number (Lk) increases during heat shock and decreases during cold shock. Despite this correspondence, plasmid DNA topology and proteins presumably involved in DNA topological control in each case are different. Plasmid DNA in hyperthermophilic archaea is found in a topo...

The superhelicity of the chromosome, which is controlled by DNA topoisomerases, modulates global gene expression. Investigations of transcriptional responses to the modulation of gyrase function have identified two types of topoisomerase-mediated transcriptional responses: (i) steady-state changes elicited by a mutation in gyrase, such as the D82G mutation in GyrA, and (ii) dynamic changes elic...

The synthesis of inducible biodegradative threonine dehydratase of Escherichia coli increased several-fold in the presence of the DNA gyrase inhibitors, nalidixic acid and coumermycin. Temperature-sensitive gyrB mutants expressed higher levels of dehydratase as compared to an isogenic gyrB+ strain. Immunoblotting experiments showed increased synthesis of the dehydratase protein in the presence ...

In Escherichia coli, the gyrase enzyme is composed of two subunits: A and B [1]. The A subunit (97 k Da) interacts and relieves DNA super coils through its active site (tyrosine) during DNA replication. The B subunit contains the ATP as active site required to release the energy in the attached ATP molecule and provides the free energy to the reaction (DNA super coiling) accomplished by the gyr...