PMID:11090135: Difference between revisions
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!align=left |Citation | |||
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'''Crisona, NJ, Strick, TR, Bensimon, D, Croquette, V and Cozzarelli, NR''' (2000) Preferential relaxation of positively supercoiled DNA by E. coli topoisomerase IV in single-molecule and ensemble measurements. ''Genes Dev.'' '''14''':2881-92 | |||
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!align=left |Abstract | |||
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We show that positively supercoiled [(+) SC] DNA is the preferred substrate for Escherichia coli topoisomerase IV (topo IV). We measured topo IV relaxation of (-) and (+) supercoils in real time on single, tethered DNA molecules to complement ensemble experiments. We find that the preference for (+) SC DNA is complete at low enzyme concentration. Otherwise, topo IV relaxed (+) supercoils at a 20-fold faster rate than (-) supercoils, due primarily to about a 10-fold increase in processivity with (+) SC DNA. The preferential cleavage of (+) SC DNA in a competition experiment showed that substrate discrimination can take place prior to strand passage in the presence or absence of ATP. We propose that topo IV discriminates between (-) and (+) supercoiled DNA by recognition of the geometry of (+) SC DNA. Our results explain how topo IV can rapidly remove (+) supercoils to support DNA replication without relaxing the essential (-) supercoils of the chromosome. They also show that the rate of supercoil relaxation by topo IV is several orders of magnitude faster than hitherto appreciated, so that a single enzyme may suffice at each replication fork. | |||
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[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11090135 PubMed] [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC317058 PMC317058] | |||
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| | !align=left |Keywords | ||
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|- | DNA Topoisomerase IV; DNA Topoisomerases, Type II/metabolism; DNA, Superhelical/metabolism; Escherichia coli/enzymology; Isomerism; Models, Genetic; Nucleic Acid Conformation; Protein Binding; Substrate Specificity | ||
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==Significance {{HelpIcon|Help:Literature}} == | ==Significance {{HelpIcon|Help:Literature}} == | ||
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==Annotations {{HelpIcon|Help:Literature}}== | ==Annotations {{HelpIcon|Help:Literature}}== | ||
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==EcoliWiki Links {{HelpIcon|Help:Literature}} == | ==EcoliWiki Links {{HelpIcon|Help:Literature}} == | ||
Latest revision as of 04:13, 15 September 2013
| Citation |
Crisona, NJ, Strick, TR, Bensimon, D, Croquette, V and Cozzarelli, NR (2000) Preferential relaxation of positively supercoiled DNA by E. coli topoisomerase IV in single-molecule and ensemble measurements. Genes Dev. 14:2881-92 |
|---|---|
| Abstract |
We show that positively supercoiled [(+) SC] DNA is the preferred substrate for Escherichia coli topoisomerase IV (topo IV). We measured topo IV relaxation of (-) and (+) supercoils in real time on single, tethered DNA molecules to complement ensemble experiments. We find that the preference for (+) SC DNA is complete at low enzyme concentration. Otherwise, topo IV relaxed (+) supercoils at a 20-fold faster rate than (-) supercoils, due primarily to about a 10-fold increase in processivity with (+) SC DNA. The preferential cleavage of (+) SC DNA in a competition experiment showed that substrate discrimination can take place prior to strand passage in the presence or absence of ATP. We propose that topo IV discriminates between (-) and (+) supercoiled DNA by recognition of the geometry of (+) SC DNA. Our results explain how topo IV can rapidly remove (+) supercoils to support DNA replication without relaxing the essential (-) supercoils of the chromosome. They also show that the rate of supercoil relaxation by topo IV is several orders of magnitude faster than hitherto appreciated, so that a single enzyme may suffice at each replication fork. |
| Links | |
| Keywords |
DNA Topoisomerase IV; DNA Topoisomerases, Type II/metabolism; DNA, Superhelical/metabolism; Escherichia coli/enzymology; Isomerism; Models, Genetic; Nucleic Acid Conformation; Protein Binding; Substrate Specificity |
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