Department of Metabolism, Digestion and Reproduction, Faculty of Medicine, Imperial College London, London W12 0NN, United Kingdom.
Molecular and Cellular Sciences Section, Neuroscience and Cell Biology Research Institute, St. George's, University of London, London SW17 0RE, United Kingdom.
Proc Natl Acad Sci U S A. 2024 Oct 8;121(41):e2413357121. doi: 10.1073/pnas.2413357121. Epub 2024 Oct 3.
Metal ions have important roles in supporting the catalytic activity of DNA-regulating enzymes such as topoisomerases (topos). Bacterial type II topos, gyrases and topo IV, are primary drug targets for fluoroquinolones, a class of clinically relevant antibacterials requiring metal ions for efficient drug binding. While the presence of metal ions in topos has been elucidated in biochemical studies, accurate location and assignment of metal ions in structural studies have historically posed significant challenges. Recent advances in X-ray crystallography address these limitations by extending the experimental capabilities into the long-wavelength range, exploiting the anomalous contrast from light elements of biological relevance. This breakthrough enables us to confirm experimentally the locations of Mg in the fluoroquinolone-stabilized topo IV complex. Moreover, we can unambiguously identify the presence of K and Cl ions in the complex with one pair of K ions functioning as an additional intersubunit bridge. Overall, our data extend current knowledge on the functional and structural roles of metal ions in type II topos.
金属离子在支持 DNA 调节酶（如拓扑异构酶）的催化活性方面发挥着重要作用。细菌 II 型拓扑异构酶、回旋酶和拓扑异构酶 IV 是氟喹诺酮类药物的主要药物靶点，这类具有临床相关性的抗生素需要金属离子才能有效结合药物。虽然生物化学研究已经阐明了拓扑异构酶中金属离子的存在，但在结构研究中准确确定和分配金属离子一直以来都具有很大的挑战性。X 射线晶体学的最新进展通过将实验能力扩展到长波长范围，利用生物相关轻元素的反常对比，解决了这些限制。这一突破使我们能够通过实验证实氟喹诺酮稳定的拓扑异构酶 IV 复合物中镁的位置。此外，我们还可以明确地确定复合物中钾离子和氯离子的存在，其中一对钾离子作为额外的亚基间桥发挥作用。总的来说，我们的数据扩展了当前关于金属离子在 II 型拓扑异构酶中功能和结构作用的知识。
