Hansen Guido, Harrenga Axel, Wieland Bernd, Schomburg Dietmar, Reinemer Peter
Bayer HealthCare AG, Pharma R and D Europe, Enabling Technologies, D-42096 Wuppertal, Germany.
J Mol Biol. 2006 May 19;358(5):1328-40. doi: 10.1016/j.jmb.2006.03.012. Epub 2006 Mar 23.
DNA topoisomerases are a family of enzymes altering the topology of DNA by concerted breakage and rejoining of the phosphodiester backbone of DNA. Bacterial and archeal type IA topoisomerases, including topoisomerase I, topoisomerase III, and reverse gyrase, are crucial in regulation of DNA supercoiling and maintenance of genetic stability. The crystal structure of full length topoisomerase I from Thermotoga maritima was determined at 1.7A resolution and represents an intact and fully active bacterial topoisomerase I. It reveals the torus-like structure of the conserved transesterification core domain comprising domains I-IV and a tightly associated C-terminal zinc ribbon domain (domain V) packing against domain IV of the core domain. The previously established zinc-independence of the functional activity of T.maritima topoisomerase I is further supported by its crystal structure as no zinc ion is bound to domain V. However, the structural integrity is preserved by the formation of two disulfide bridges between the four Zn-binding cysteine residues. A functional role of domain V in DNA binding and recognition is suggested and discussed in the light of the structure and previous biochemical findings. In addition, implications for bacterial topoisomerases I are provided.
DNA拓扑异构酶是一类通过协同断裂和重新连接DNA的磷酸二酯主链来改变DNA拓扑结构的酶。细菌和古细菌的IA型拓扑异构酶，包括拓扑异构酶I、拓扑异构酶III和反向回旋酶，在DNA超螺旋的调节和遗传稳定性的维持中起着关键作用。嗜热栖热菌全长拓扑异构酶I的晶体结构在1.7埃分辨率下被确定，它代表了一个完整且完全活跃的细菌拓扑异构酶I。它揭示了保守的转酯核心结构域的环状结构，该结构域由结构域I-IV和一个紧密相连的C末端锌带结构域（结构域V）组成，结构域V靠在核心结构域的结构域IV上。嗜热栖热菌拓扑异构酶I功能活性先前确定的锌非依赖性在其晶体结构中得到进一步支持，因为没有锌离子与结构域V结合。然而，通过四个锌结合半胱氨酸残基之间形成两个二硫键，结构完整性得以保留。根据结构和先前的生化研究结果，提出并讨论了结构域V在DNA结合和识别中的功能作用。此外，还提供了对细菌拓扑异构酶I的启示。
