Forterre P, Elie C, Sioud M, Hamal A
Institut de Microbiologie, Université Paris-Sud, France.
Can J Microbiol. 1989 Jan;35(1):228-33. doi: 10.1139/m89-035.
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.
嗜酸热硫化叶菌和嗜酸嗜热栖热菌中分离出了DNA聚合酶和拓扑异构酶。这些DNA聚合酶分别由分子量为100 kDa和85 kDa的单一多肽组成。针对嗜酸热硫化叶菌DNA聚合酶的抗体与嗜酸嗜热栖热菌DNA聚合酶没有交叉反应。嗜酸热硫化叶菌中的主要DNA拓扑异构酶活性是一种具有反向解旋酶活性的依赖ATP的I型DNA拓扑异构酶，而嗜酸嗜热栖热菌中的主要DNA拓扑异构酶活性是一种不依赖ATP的松弛活性。这两种酶与真细菌的I型DNA拓扑异构酶更相似，而不是与真核生物的相似。我们发现，来自嗜盐菌的小质粒是负超螺旋的，并且DNA拓扑异构酶II抑制剂会改变它们的拓扑结构。这表明存在一种与真细菌和真核生物对应物相关的古细菌II型DNA拓扑异构酶。与真细菌一样，新生霉素会诱导嗜盐菌质粒产生正超螺旋，这表明不存在能够松弛正超螺旋的类似真核生物的I型DNA拓扑异构酶。
