title: Studies on DNA polymerases and topoisomerases in archaebacteria.
abstract: We have isolated DNA polymerases and topoisomerases from two thermoacidophilic archaebacteria: Sulfolobus acidocaldarius and Thermoplasma acidophilum. The DNA polymerases are composed of a single polypeptide with molecular masses of 100 and 85 kDa, respectively. Antibodies against Sulfolobus DNA polymerase did not cross react with Thermoplasma DNA polymerase. Whereas the major DNA topoisomerase activity in S. acidocaldarius is an ATP-dependent type I DNA topoisomerase with a reverse gyrase activity, the major DNA topoisomerase activity in T. acidophilum is a ATP-independent relaxing activity. Both enzymes resemble more the eubacterial than the eukaryotic type I DNA topoisomerase. We have found that small plasmids from halobacteria are negatively supercoiled and that DNA topoisomerase II inhibitors modify their topology. This suggests the existence of an archaebacterial type II DNA topoisomerase related to its eubacterial and eukaryotic counterparts. As in eubacteria, novobiocin induces positive supercoiling of halobacterial plasmids, indicating the absence of a eukaryotic-like type I DNA topoisomerase that relaxes positive superturns.
authors.affiliation: Institut de Microbiologie, Université Paris-Sud, France.
authors.forename: P
authors.initials: P
authors.lastname: Forterre
authors.forename: C
authors.initials: C
authors.lastname: Elie
authors.forename: M
authors.initials: M
authors.lastname: Sioud
authors.forename: A
authors.initials: A
authors.lastname: Hamal
mesh_terms: D001105:Archaea / Q000201:enzymology*; D001419:Bacteria / Q000201:enzymology*; D005075:Biological Evolution; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism; D004278:DNA, Superhelical / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D008970:Molecular Weight; D010957:Plasmids; D011387:Prokaryotic Cells / Q000201:enzymology
chemical_list: D004269:DNA, Bacterial; D004278:DNA, Superhelical; D004259:DNA-Directed DNA Polymerase; C041813:DNA reverse gyrase; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II