title: DNA topoisomerase I from Diplococcus pneumoniae.
abstract: A type I topoisomerase has been purified from Diplococcus pneumoniae using phosphocellulose and hydroxylapatite chromatography. The purified enzyme catalyses the relaxation of negatively supercoiled DNA. The relaxation requires Mg2+ and is favoured by 0.2 M monovalent cations. The enzyme does not exhibit catenating or supercoiling activities. Using circular pBR322 DNA from dam+- and dam- -hosts as substrates for the enzyme, the relaxation reaction proceeds with somewhat higher efficiency with plasmids containing methylated adenine in GATC sequences. Plasmids from dcm+- and dcm- -hosts show no difference in reactivity.
authors.affiliation: Akademie der Wissenschaften der DDR.
authors.forename: K
authors.initials: K
authors.lastname: Störl
authors.forename: H J
authors.initials: HJ
authors.lastname: Störl
mesh_terms: D002845:Chromatography; D002852:Chromatography, Ion Exchange; D004264:DNA Topoisomerases, Type I / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D017886:Durapatite; D004926:Escherichia coli / Q000235:genetics; D006882:Hydroxyapatites; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D010957:Plasmids; D013296:Streptococcus pneumoniae / Q000201:enzymology* / Q000235:genetics; D013816:Thermodynamics; D014169:Transformation, Bacterial
chemical_list: D006882:Hydroxyapatites; D017886:Durapatite; D004264:DNA Topoisomerases, Type I; D008274:Magnesium