STUDIES OF FUNCTIONS INVOLVED IN GENETIC RECOMBINATION

嗜热菌中一种新的拓扑异构酶（拓扑异构酶V） 古细菌已被证明具有与真核生物相似的性质， 拓扑异构酶，与其他细菌酶非常不同， 课 它使负或正超螺旋DNA松弛， 不依赖于二价金属离子的反应，连接到3'端 并显示出与抗体的显著交叉反应性 针对人类拓扑异构酶I的 一种进化关系， 古细菌和真核生物经常被讨论; 这种酶支持这个想法。 在对DNA促旋酶的进一步研究中，ATP结合位点的突变 已被用来表明，两个B亚单位在活性A2 B2复合物必须 能够水解ATP以使酶催化DNA 超螺旋 转录自E。受DNA刺激的大肠杆菌启动子 弛豫还能够读取通过终止信号， 距离，这种通读进一步增加了DNA 放松. 不同地点的事件之间的这种耦合是证据 RNA聚合酶以外的其他因子的使用。 一种用于这种检测的方法， 因子已经被设计出来，现在正被用于纯化方案。

A novel topoisomerase (topoisomerase V) from a thermophilic archaebacterium has been shown to have properties similar to eukaryotic topoisomerases and quite distinct from other bacterial enzymes of this class. It relaxes either negatively or positively supercoiled DNA in a reaction not dependent on a divalent metal ion, attaches to the 3' end of the DNA chain, and shows a striking cross-reactivity with antibody against human topoisomerase I. An evolutionary relationship between archaebacteria and eukaryotes has often been discussed; the properties of this enzyme support the idea. In further studies of DNA gyrase, mutations of the ATP binding site have been used to show that both B subunits in the active A2B2 complex must be capable of hydrolyzing ATP in order for the enzyme to catalyze DNA supercoiling. Transcription from E. coli promoters that are stimulated by DNA relaxation is also able to read through termination signals some distance away, and this readthrough is further increased by DNA relaxation. This coupling between events at separated sites is evidence for the use of other factors beside RNA polymerase. An assay for such factors has been devised and is now being used in a purification scheme.