title: Purification and properties of a topoisomerase from Ustilago maydis.
abstract: The lower eukaryote Ustilago maydis contains a topoisomerase that removes supercoils from negative and positive superhelical DNA. The enzyme may be a multimeric protein or an aggregate of polypeptides with a native molecular weight of 270,000 as estimated by gel filtration. No cofactors are required by the enzyme, but activity is enhanced by Mg2+. Dependence of activity upon enzyme concentration is not linear. Below a threshold level where topoisomerase cannot ordinarily be detected, addition of H1 histone sharply stimulates activity. ATP and a number of structural analogues inhibit the enzyme.
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001487:Basidiomycota / Q000201:enzymology*; D004264:DNA Topoisomerases, Type I / Q000302:isolation & purification* / Q000378:metabolism; D004789:Enzyme Activation; D006657:Histones / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008970:Molecular Weight; D011119:Polynucleotides / Q000494:pharmacology; D012265:Ribonucleotides / Q000494:pharmacology; D014588:Ustilago / Q000201:enzymology*
chemical_list: D000900:Anti-Bacterial Agents; D006657:Histones; D011119:Polynucleotides; D012265:Ribonucleotides; D004264:DNA Topoisomerases, Type I; D008274:Magnesium