Untangling topoisomerase inhibition by protein toxins through cryo-electron microscopy and crystallography

结核分枝杆菌（Mtb）感染了世界三分之一的人口，2015年造成180万人死亡，超过艾滋病毒成为最致命的人类病原体。我们最近展示了临床使用的氟喹诺酮类抗生素（全球销售额约80亿美元）如何抑制结核杆菌的DNA回转酶，这是DNA复制和维持DNA超卷曲所必需的基本拓扑异构酶。这项工作还强调了抗生素耐药性如何使氟喹诺酮类药物无效。从毒素-抗毒素系统中，有大量的替代天然抗生素可以靶向DNA旋切酶。结核分枝杆菌编码至少80种不同的毒素-抗毒素基因座，这些基因座发挥多种作用，如通过特异性地阻止细胞生长来保护宿主巨噬细胞免受抗生素侵害和控制其休眠。这些基因座包括parDE家族的同源物，它们抑制DNA回转酶。我们建议研究ParE毒素抑制DNA旋切酶的生化和结构基础。研究这些复合物将产生新的方法来抑制经过数千年细菌进化验证的毒素的治疗靶点。

Mycobacterium tuberculosis (Mtb) infects one-third of the world's population and in 2015 accounted for 1.8 million deaths, overtaking HIV as the most deadly human pathogen. We have recently demonstrated how clinically-utilised fluoroquinolone antibiotics (global sales ~$8 bn) inhibit DNA gyrase from Mtb, an essential topoisomerase necessary for DNA replication and maintenance of DNA supercoiling. This work also highlighted how antibiotic resistance is rendering fluoroquinolones ineffective. There is an abundance of alternative naturally-occurring antibiotics, from toxin-antitoxin systems, that can target DNA gyrase. Mtb encodes at least eighty different toxin-antitoxin loci, which perform multiple roles such as protection from antibiotics and controlling dormancy inside host macrophages, by specifically halting cell growth. These loci include homologues of the parDE family, which inhibit DNA gyrase. We propose to study the biochemical and structural basis of DNA gyrase inhibition by ParE toxins. Studying these complexes will generate new ways to inhibit a proven therapeutic target using toxins validated by millennia of bacterial evolution.