File Name: dna gyrase structure and function .zip
State of the Art Antiviral agents are the pharmacological agents used against virus infections. They are used in order to control or destroy the viral infection. Currently existing antiviral therapies are the methods for temporarily suppressing the symptoms caused by the virus, rather than the virus itself, by way of suppression of the enzymes that regulate the capabilities of the viruses to self-replicate and to synthesize DNA from RNA.
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Manjunatha, M. Dalal, M. Chatterji, D. Radha, S. Visweswariah, V. A rapid single step immunoaffinity purification procedure is described for Mycobacterium smegmatis DNA gyrase. The mycobacterial enzyme is a kDa heterotetrameric protein comprising two subunits each of GyrA and GyrB, exhibiting subtle differences and similarities to the well-characterised Escherichia coli gyrase.
Metrics details. DNA gyrase, an enzyme once thought to be unique to bacteria, is also found in some eukaryotic plastids including the apicoplast of Apicomplexa such as Plasmodium falciparum and Toxoplasma gondii which are important disease-causing organisms. DNA gyrase is an excellent target for antibacterial drugs, yet such antibacterials seem ineffective against Apicomplexa. Characterisation of the apicoplast gyrases would be a useful step towards understanding why this should be so. While purification of active apicoplast gyrase has proved impossible to date, in silico analyses have allowed us to discover differences in the apicoplast proteins.
For a cell to complete DNA replication, every link between the Watson-Crick strands must be removed by topoisomerases. Using pulse labeling with [3H]thymidine in Escherichia coli, we have found that in the absence of topo IV activity, nearly all newly synthesized plasmid DNA is catenated. Pulse-chase protocols revealed that catenanes are metabolized even in the absence of topo IV and that the residual turnover is carried out by DNA gyrase at a rate of approximately 0. Using extremely short pulse-labeling times, we identified significant amounts of replication catenanes in wild-type cells. Therefore, gyrase is fold less efficient than topo IV in plasmid replicon decatenation in vivo. This may explain why a fully functional gyrase cannot prevent the catenation of newly synthesized plasmid DNA and the partition phenotype of topo IV mutants.
Mycobacterium tuberculosis DNA gyrase, an indispensable nanomachine involved in the regulation of DNA topology, is the only type II topoisomerase present in this organism and is hence the sole target for quinolone action, a crucial drug active against multidrug-resistant tuberculosis. To understand at an atomic level the quinolone resistance mechanism, which emerges in extensively drug resistant tuberculosis, we performed combined functional, biophysical and structural studies of the two individual domains constituting the catalytic DNA gyrase reaction core, namely the Toprim and the breakage-reunion domains. This allowed us to produce a model of the catalytic reaction core in complex with DNA and a quinolone molecule, identifying original mechanistic properties of quinolone binding and clarifying the relationships between amino acid mutations and resistance phenotype of M. These results are compatible with our previous studies on quinolone resistance. Interestingly, the structure of the entire breakage-reunion domain revealed a new interaction, in which the Q uinolone- B inding P ocket QBP is blocked by the N-terminal helix of a symmetry-related molecule. This interaction provides useful starting points for designing peptide based inhibitors that target DNA gyrase to prevent its binding to DNA.
DNA gyrase , or simply gyrase , is an enzyme within the class of topoisomerase and is a subclass of Type II topoisomerases  that reduces topological strain in an ATP dependent manner while double-stranded DNA is being unwound by elongating RNA-polymerase  or by helicase in front of the progressing replication fork. It does so by looping the template so as to form a crossing, then cutting one of the double helices and passing the other through it before releasing the break, changing the linking number by two in each enzymatic step. This process occurs in bacteria , whose single circular DNA is cut by DNA gyrase and the two ends are then twisted around each other to form supercoils. Gyrase is also found in eukaryotic plastids : it has been found in the apicoplast of the malarial parasite Plasmodium falciparum   and in chloroplasts of several plants. The unique ability of gyrase to introduce negative supercoils into DNA at the expense of ATP hydrolysis  is what allows bacterial DNA to have free negative supercoils.
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of double-stranded closed-circular DNA. Gyrase belongs to a class of enzymes known as topoisomerases that are involved in the control of topological transitions.Reply