Institute of Nanoscience and Nanotechnology, NCSR "Demokritos", Ag. Paraskevi, 15310, Athens, Greece.
Le Studium Loire Valley Institute for Advanced Studies, Orléans, France.
Commun Biol. 2022 Feb 9;5(1):120. doi: 10.1038/s42003-022-03069-6.
The bacterial Rho factor is a ring-shaped motor triggering genome-wide transcription termination and R-loop dissociation. Rho is essential in many species, including in Mycobacterium tuberculosis where rho gene inactivation leads to rapid death. Yet, the M. tuberculosis Rho [Rho] factor displays poor NTPase and helicase activities, and resistance to the natural Rho inhibitor bicyclomycin [BCM] that remain unexplained. To address these issues, we solved the cryo-EM structure of Rho at 3.3 Å resolution. The Rho hexamer is poised into a pre-catalytic, open-ring state wherein specific contacts stabilize ATP in intersubunit ATPase pockets, thereby explaining the cofactor preference of Rho. We reveal a leucine-to-methionine substitution that creates a steric bulk in BCM binding cavities near the positions of ATP γ-phosphates, and confers resistance to BCM at the expense of motor efficiency. Our work contributes to explain the unusual features of Rho and provides a framework for future antibiotic development.
细菌 Rho 因子是一种环形分子马达，可引发全基因组转录终止和 R 环解离。Rho 因子在许多物种中都很重要，包括结核分枝杆菌，在该菌中，rho 基因突变会导致快速死亡。然而，结核分枝杆菌 Rho [Rho]因子的 NTPase 和解旋酶活性较差，且对天然 Rho 抑制剂双环霉素 [BCM]具有抗性，这些特性仍未得到解释。为了解决这些问题，我们解析了 Rho 的冷冻电镜结构，分辨率为 3.3Å。Rho 六聚体处于预催化的开环状态，其中特定的接触稳定了亚基间 ATPase 口袋中的 ATP，从而解释了 Rho 对辅助因子的偏好。我们揭示了一个亮氨酸到蛋氨酸的取代，在靠近 ATP γ-磷酸位置的 BCM 结合腔内形成了空间位阻，从而导致对 BCM 的抗性，牺牲了马达效率。我们的工作有助于解释 Rho 的异常特征，并为未来抗生素的开发提供了框架。
