Villa Héctor, Otero Marcos Ana R, Reguera Rosa M, Balaña-Fouce Rafael, García-Estrada Carlos, Pérez-Pertejo Yolanda, Tekwani Babu L, Myler Peter J, Stuart Kenneth D, Bjornsti Mary-Ann, Ordóñez David
Departamento de Farmacologia y Toxicologia (INTOXCAL), Universidad de León, Campus de Vegazana sn, 24071 León, Spain.
J Biol Chem. 2003 Feb 7;278(6):3521-6. doi: 10.1074/jbc.M203991200. Epub 2002 Nov 19.
A common feature shared by type I DNA topoisomerases is the presence of a "serine, lysine, X, X, tyrosine" motif as conventional enzyme active site. Preliminary data have shown that Leishmania donovani DNA topoisomerase I gene (LdTOP1A) lacked this conserved motif, giving rise to different theories about the reconstitution of an active DNA topoisomerase I in this parasite. We, herein, describe the molecular cloning of a new DNA topoisomerase I gene from L. donovani (LdTOP1B) containing the highly conserved serine, lysine, X, X, tyrosine motif. DNA topoisomerase I activity was detected only when both genes (LdTOP1A and LdTOP1B) were co-expressed in a yeast expression system, suggesting the existence of a dimeric DNA topoisomerase I in Leishmania parasites.
I型DNA拓扑异构酶的一个共同特征是存在一个“丝氨酸、赖氨酸、X、X、酪氨酸”基序作为传统的酶活性位点。初步数据表明，杜氏利什曼原虫DNA拓扑异构酶I基因（LdTOP1A）缺乏这种保守基序，这引发了关于该寄生虫中活性DNA拓扑异构酶I重组的不同理论。在此，我们描述了从杜氏利什曼原虫中克隆出的一个新的DNA拓扑异构酶I基因（LdTOP1B），它含有高度保守的丝氨酸、赖氨酸、X、X、酪氨酸基序。只有当这两个基因（LdTOP1A和LdTOP1B）在酵母表达系统中共同表达时，才能检测到DNA拓扑异构酶I的活性，这表明利什曼原虫寄生虫中存在二聚体DNA拓扑异构酶I。
