Sulfolobus topoisomerase

Life in a hot tub. An archaeon (Sulfolobus acidocaldarius) found in acidic hot springs contains a topoisomerase that catalyzes the ATP-driven introduction of positive supercoils into DNA. How might this enzyme be advantageous to this unusual organism ... 

In their first paper, Kikuchi and Asai [72] reported that S. acidocaldarius contained, besides a reverse gyrase, one ATP-independent and two ATP-dependent thermophilic DNA topoisomerases (including one DNA gyrase). However, their purification procedure lacked a step to remove DNA, so that at least one of the ATP-dependent topoisomerases probably corresponded to the reverse gyrase copurifying with DNA (discussed in ref [74]). Later work did not confirm the presence of a classical gyrase but demonstrated the presence of at least one type II DNA topoisomerase, and probably one ATP-independent type I DNA topoisomerase in Sulfolobus and in other thermophilic archaebacteria. 

The unknotting reaction (typical of type II DNA topoisomerases) is ten times more efficient than relaxation. The most purified fraction contained two major polypeptides of 40 and 60 kDa. The S. acidocaldarius type II DNA topoisomerase has no DNA gyrase activity. This suggested that it could specifically resemble the eukaryotic type II DNA topoisomerase however, taking into account its putative dimeric structure, it could also resemble the new type II DNA topoisomerase (topo IV) recently discovered in E. co/i [70]. We have recently detected in our laboratory a type II DNA topoisomerase in Sulfolobus shibatae. This enzyme catalyzes the same reactions as the enzyme from Sulfolobus solfataricus and exhibits a pattern of drug sensitivity very similar to that of the eukaryotic enzyme [Bergerat, A., this laboratory]. 

At the moment, the overall pattern of DNA topology and DNA topoisomerases in archaebacteria is clearly more similar to the eubacterial one than to the eukaryotic one (Table 2). One can speculate that the similarities between DNA topology in eubacteria and archaebacteria are related to the presence of the same type of prokaryotic chromosomal organization in these two domains. An exception to this pattern is the presence of a type II DNA topoisomerase without gyrase activity in Sulfolobus. It remains to be determined whether the latter enzyme is indeed specifically related to the eukaryotic type II DNA topoisomerases or to E. coli DNA topoisomerase IV, and which kinds of type II DNA topoisomerases exist in other sulfothermophiles and methanogens. 

Bacterial DNA topoisomerase I II Yeast DNA topoisomerase III DNA topoisomerase Ilia and III Mammalian DNA topoisomerase Ilia and III Vaccinia and Pox vims monomeric topo I Kinetoplastida bi-subunit topoisomerase I Mammalian mitochondrial topoisomerase I Eukaryotic monomeric topoisomerase I Bacterial gyrase, DNA topoisomerase IV Phage T4 DNA topoismnerase Yeast DNA topoisomerase II Drosophila DNA topoisomerase II Mammalian DNA topoisomerase Ha and lip Sulfolobus shibate DNA topoisomerase VI (subunit A honwiogous to yeast SP011)... 

Two DNA topoisomerases VI have been purified to homogeneity from archaeal strains. The first purification reported was that of the enzyme from Sulfolobus shibatae, an extremely thermophilic crenoarchaeota with an optimal growth temperature of 85°. This article presents the purification of the DNA topoisomerase VI from Pyrococcus furiosus, an extremely thermophilic anaerobic euryarchaeota with an optimal growth temperature of 95°. These two enzymes share many properties and can be purified by a similar procedure. However, the purification of the DNA topoisomerase VI from P. furiosus has been simplified and some modifications, required by the extreme thermophily of this enzyme, have been introduced into DNA topoisomerase assays. Finally, physical and enzymatic properties of DNA topoisomerase VI are discussed. 

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