title: The N-terminal domain of human topoisomerase IIalpha is a DNA-dependent ATPase.
abstract: We have constructed clones encoding N-terminal fragments of human DNA topoisomerase IIalpha. We show that the N-terminal domain (approximately 50 kDa) has an intrinsic ATPase activity that can be stimulated by DNA. The enzyme obeys Michaelis-Menten kinetics showing a approximately 6-fold increase in kcat in the presence of DNA. Cross-linking studies indicate that the N-terminal domain is a dimer in the absence and presence of nucleotides. Using site-directed mutagenesis, we have identified the catalytic residue for ATP hydrolysis as Glu86. Phosphorylation of the N-terminal domain with protein kinase C does not affect the ATPase activity. The ATPase domain of human topoisomerase IIalpha shows significant differences from its counterpart in DNA gyrase and we discuss the mechanistic implications of these data.
authors.affiliation: Department of Biochemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom.
authors.forename: L P
authors.initials: LP
authors.lastname: Gardiner
authors.forename: D I
authors.initials: DI
authors.lastname: Roper
authors.forename: T R
authors.initials: TR
authors.lastname: Hammonds
authors.forename: A
authors.initials: A
authors.lastname: Maxwell
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000951:Antigens, Neoplasm; D020134:Catalytic Domain / Q000235:genetics; D003001:Cloning, Molecular; D004265:DNA Helicases; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D006868:Hydrolysis; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D000951:Antigens, Neoplasm; D004268:DNA-Binding Proteins; D007527:Isoenzymes; D010446:Peptide Fragments; D011994:Recombinant Proteins; D000251:Adenosine Triphosphatases; D004265:DNA Helicases; D004250:DNA Topoisomerases, Type II