Both DNA Gyrase and Reverse Gyrase are Present in the Hyperthermophilic Bacterium Thermotoga maritima

• Published in: Proceedings of the National Academy of Sciences - PNAS 1997-09, Vol.94 (20), p.10606-10611
• Main Authors: Guipaud, Olivier, Marguet, Evelyne, Noll, Kenneth M., De La Tour, Claire Bouthier, Forterre, Patrick
• Format: Article
• Language: English
• Subjects: Archaea; Bacteria; Bacteriology; Biochemistry; Biological Sciences; Cloning, Molecular; Deoxyribonucleic acid; DNA; DNA Topoisomerases, Type II - genetics; DNA Topoisomerases, Type II - metabolism; DNA, Bacterial - chemistry; DNA, Bacterial - drug effects; DNA, Superhelical - chemistry; DNA, Superhelical - drug effects; Enzymes; Gels; Genomics; Gram-Negative Anaerobic Bacteria - enzymology; Mathematical topoi; Molecular Sequence Data; Novobiocin - pharmacology; Plasmids; Proteins; Thermotoga maritima; Topology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.94.20.10606

Like all hyperthermophiles yet tested, the bacterium Thermotoga maritima contains a reverse gyrase. Here we show that it contains also a DNA gyrase. The genes top2A and top2B encoding the two subunits of a DNA gyraselike enzyme have been cloned and sequenced. The Top2A (type II DNA topoisomerase A protein) is more similar to GyrA (DNA gyrase A protein) than to ParC [topoisomerase IV (Topo IV) C protein]. The difference is especially striking at the C-terminal domain, which differentiates DNA gyrases from Topo IV. DNA gyrase activity was detected in T. maritima and purified to homogeneity using a novobiocin-Sepharose column. This hyperhermophilic DNA gyrase has an optimal activity around 82-86 degrees C. In contrast to plasmids from hyperthermophilic archaea, which are from relaxed to positively supercoiled, we found that the plasmid pRQ7 from Thermotoga sp. RQ7 is negatively supercoiled. pRQ7 became positively supercoiled after addition of novobiocin to cell cultures, indicating that its negative supercoiling is due to the DNA gyrase of the host strain. The findings concerning DNA gyrase and negative supercoiling in Thermotogales put into question the role of reverse gyrase in hyperthermophiles.