title: DNA topoisomerase III from extremely thermophilic archaebacteria. ATP-independent type I topoisomerase from Desulfurococcus amylolyticus drives extensive unwinding of closed circular DNA at high temperature.
abstract: A second type I topoisomerase was purified from the extremely thermophilic archaebacterium Desulfurococcus amylolyticus. In contrast to the previously described reverse gyrase from this organism, the novel enzyme designated as Dam topoisomerase III is an ATP-independent relaxing topoisomerase. It is a monomer with Mr 108,000, as determined by electrophoresis under denaturing conditions and by size exclusion chromatography. Dam topoisomerase III, like other bacterial type I topoisomerases, absolutely requires Mg2+ for activity and is specific for single-stranded DNA. At 60-80 degrees C, it relaxes negatively but not positively supercoiled DNA and is inhibited by single-stranded M13 DNA. At 95 degrees C, the enzyme unwinds both positively and negatively supercoiled substrates and produces extensively unwound form I* and I** DNA. The peculiarities of DNA topoisomerization at high temperatures are discussed.
authors.affiliation: Institute of Molecular Genetics, Union of Soviet Socialist Republics Academy of Sciences, Moscow.
authors.forename: A I
authors.initials: AI
authors.lastname: Slesarev
authors.forename: D A
authors.initials: DA
authors.lastname: Zaitzev
authors.forename: V M
authors.initials: VM
authors.lastname: Kopylov
authors.forename: K O
authors.initials: KO
authors.lastname: Stetter
authors.forename: S A
authors.initials: SA
authors.lastname: Kozyavkin
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D001105:Archaea / Q000201:enzymology*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry*; D004270:DNA, Circular / Q000737:chemistry*; D004278:DNA, Superhelical / Q000737:chemistry; D004587:Electrophoresis, Agar Gel; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D009690:Nucleic Acid Conformation; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013696:Temperature
chemical_list: D004269:DNA, Bacterial; D004270:DNA, Circular; D004278:DNA, Superhelical; D000255:Adenosine Triphosphate; D012964:Sodium; C041813:DNA reverse gyrase; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II; D011188:Potassium