title: An atypical type II topoisomerase from Mycobacterium smegmatis with positive supercoiling activity.
abstract: Topoisomerases are essential ubiquitous enzymes, falling into two distinct classes. A number of eubacteria including Escherichia coli, typically contain four topoisomerases, two type I topoisomerases and two type II topoisomerases viz. DNA gyrase and topoisomerase IV. In contrast several other bacterial genomes including mycobacteria, encode for one type I topoisomerase and a DNA gyrase. Here we describe a new type II topoisomerase from Mycobacterium smegmatis which is different from DNA gyrase or topoisomerase IV in its characteristics and origin. The topoisomerase is distinct with respect to domain organization, properties and drug sensitivity. The enzyme catalyses relaxation of negatively supercoiled DNA in an ATP-dependent manner and also introduces positive supercoils to both relaxed and negatively supercoiled substrates. The genes for this additional topoisomerase are not found in other sequenced mycobacterial genomes and may represent a distant lineage.
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Paras
authors.initials: P
authors.lastname: Jain
authors.forename: Valakunja
authors.initials: V
authors.lastname: Nagaraja
mesh_terms: D002939:Ciprofloxacin / Q000494:pharmacology; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004278:DNA, Superhelical / Q000378:metabolism*; D004586:Electrophoresis / Q000379:methods; D015180:Electrophoresis, Gel, Two-Dimensional; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020102:Mycobacterium smegmatis / Q000201:enzymology* / Q000235:genetics; D009675:Novobiocin / Q000494:pharmacology; D010802:Phylogeny; D059005:Topoisomerase II Inhibitors
chemical_list: D004278:DNA, Superhelical; D004791:Enzyme Inhibitors; D059005:Topoisomerase II Inhibitors; D009675:Novobiocin; D002939:Ciprofloxacin; D004250:DNA Topoisomerases, Type II