Department of Structural & Chemical Biology, Centro de Investigaciones Biológicas Margarita Salas, CSIC, Madrid, 28040, Spain.
Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
Nat Commun. 2023 Apr 22;14(1):2335. doi: 10.1038/s41467-023-38071-x.
Transposases are ubiquitous enzymes that catalyze DNA rearrangement events with broad impacts on gene expression, genome evolution, and the spread of drug-resistance in bacteria. Here, we use biochemical and structural approaches to define the molecular determinants by which IstA, a transposase present in the widespread IS21 family of mobile elements, catalyzes efficient DNA transposition. Solution studies show that IstA engages the transposon terminal sequences to form a high-molecular weight complex and promote DNA integration. A 3.4 Å resolution structure of the transposase bound to transposon ends corroborates our biochemical findings and reveals that IstA self-assembles into a highly intertwined tetramer that synapses two supercoiled terminal inverted repeats. The three-dimensional organization of the IstA•DNA cleaved donor complex reveals remarkable similarities with retroviral integrases and classic transposase systems, such as Tn7 and bacteriophage Mu, and provides insights into IS21 transposition.
转座酶是普遍存在的酶，能催化 DNA 重排事件，对基因表达、基因组进化和细菌耐药性的传播有广泛影响。在这里，我们使用生化和结构方法来定义 IstA（一种存在于广泛的 IS21 家族移动元件中的转座酶）催化有效 DNA 转座的分子决定因素。溶液研究表明，IstA 与转座子末端序列结合形成高分子量复合物，并促进 DNA 整合。3.4 Å 分辨率的转座酶结合转座子末端的结构证实了我们的生化发现，并揭示了 IstA 自我组装成一个高度交织的四聚体，连接两个超螺旋末端反向重复序列。IstA•DNA 切割供体复合物的三维结构与逆转录病毒整合酶和经典转座酶系统（如 Tn7 和噬菌体 Mu）具有显著相似性，并为 IS21 转座提供了见解。
