Molecular basis of DNA gating by topo IV and gyrase and its inhibition by antimicrobial drugs

大多数生命形式，无论是人类、哺乳动物、酵母还是细菌，都有DNA基因组。DNA由两条相互缠绕形成标志性DNA螺旋的链组成。在DNA复制过程中，螺旋必须解开才能进行复制和染色体分离。这一过程会产生DNA超螺旋和DNA缠结，从而阻止复制。拓扑异构酶通过在DNA中引入瞬时的单链或双链断裂来解决“解卷问题”，这些断裂可以驱散超级螺旋，使DNA合成得以进行。拓扑异构酶是必不可少的酶，这并不令人惊讶，但事实证明，它们也是抑制细胞生长的抗菌和抗癌药物的重要靶点。我们的目标是使用生化和X射线结晶学的方法来研究两种细菌拓扑异构酶，即Topo IV和旋转酶。我们希望了解这些蛋白质在分子水平上是如何发挥作用的，以及氟喹诺酮类等临床重要药物是如何针对它们的功能的。这项工作将集中在肺炎链球菌的TOPO IV和旋转酶上，这是一种危险的人类病原体，会导致危及生命的肺炎和脑膜炎。然而，这项研究在其他细菌和微生物系统中有更广泛的应用。这一关键领域的进展应该有助于开发对抗生素耐药生物有效的新药，抗生素耐药生物对我们的医疗体系构成越来越大的威胁。

Most life-forms whether humans, mammals, yeast or bacteria have a DNA genome. The DNA consists of two strands that wrap around each other to form the iconic DNA helix. During DNA replication, the helix must be unwound to allow copying and chromosome segregation. This process generates DNA supercoils and DNA tangles that can block replication. Topoisomerases solve the 'unwinding problem' by introducing transient single- or double-stranded breaks into DNA that dissipate supercoils and allow DNA synthesis to proceed. It is not surprising that topoisomerases are essential enzymes but they also turn out to be vital targets of antibacterial and anticancer drugs that inhibit cell growth. We aim to use biochemical and X-ray crystallographic approaches to study two bacterial topoisomerases called topo IV and gyrase. We wish to understand how these proteins act at the molecular level and how clinically important drugs such as fluoroquinolones target their functions. The work will focus on the well-characterised topo IV and gyrase from Streptococcus pneumoniae, a dangerous human pathogen that causes life-threatening pneumonia and meningitis. However the research has wider applications to other bacterial and microbial systems. Progress in this key area should aid development of new drugs that work against antibiotic-resistant organisms, a growing threat to our healthcare system.