Gómez-Eichelmann M C, Camacho-Carranza R
Departamento de Biología Molecular, Universidad Nacional Autónoma de México.
Rev Latinoam Microbiol. 1995 Jul-Sep;37(3):291-304.
The chromosomal DNA of all cells is under helical tension or supercoiling. There are two classes of DNA supercoiling: plectonemic and toroidal. Plectonemic supercoiling is generated by the action of DNA topoisomerases, while toroidal supercoiling is generated by DNA-protein interactions and by topoisomerase activitities. DNA supercoiling plays an important role in replication, repair, recombination, transposition and transcription. DNA topoisomerases type I are ATP-independent enzymes that cut one DNA strand and relax supercoiled molecules. DNA topoisomerases type II requiere ATP, cut both DNA strands and supercoil relaxed molecules. All organisms have more than one topoisomerase of each, type I and type II. Escherichia coli has two topoisomerases type I: topoisomerase I and topoisomerase III and two topoisomerases type II: topoisomerase II or gyrase and topoisomerase IV. In this review we discuss the concept of DNA supercoiling and present current knowledge on E. coli DNA topoisomerases.
所有细胞的染色体DNA都处于螺旋张力或超螺旋状态。DNA超螺旋有两类：扭结型和环形。扭结型超螺旋是由DNA拓扑异构酶的作用产生的，而环形超螺旋是由DNA-蛋白质相互作用和拓扑异构酶活性产生的。DNA超螺旋在复制、修复、重组、转座和转录中起重要作用。I型DNA拓扑异构酶是不依赖ATP的酶，它切割一条DNA链并使超螺旋分子松弛。II型DNA拓扑异构酶需要ATP，切割两条DNA链并使松弛的分子超螺旋化。所有生物都有不止一种I型和II型拓扑异构酶。大肠杆菌有两种I型拓扑异构酶：拓扑异构酶I和拓扑异构酶III，以及两种II型拓扑异构酶：拓扑异构酶II或促旋酶和拓扑异构酶IV。在这篇综述中，我们讨论了DNA超螺旋的概念，并介绍了关于大肠杆菌DNA拓扑异构酶的当前知识。
