Recognition, opening and stabilization of DNA gates by topo IV the chromosome decatenase

topo IV酶介导细菌染色体在细胞分裂时分离之前的解缠。Topo IV通过一个DNA螺旋穿过另一个，允许分离拓扑上连锁的染色体。它通过一种不寻常的机制做到这一点：它在一个分子中制造一个短暂的双链DNA断裂（通常称为“门”），使第二个DNA分子通过。抗菌喹诺酮类药物的作用是稳定打开的DNA门，从而干扰DNA复制，导致细胞死亡。事实上，喹诺酮类药物现在是治疗肺炎和其他由肺炎链球菌和其他革兰氏阳性病原体引起的感染的重要药物。尽管它具有科学意义和医学重要性，但对topo IV的机制及其药物相互作用知之甚少。在这项研究中，我们的目标是研究(i)肺炎链球菌topo IV如何识别和打开DNA中的潜在门序列，以及（ii）喹诺酮类药物如何稳定这些门。这项工作将利用我们在肺炎链球菌染色体上发现的已知topo IV门的合成和改变版本。我们还将研究突变topo IV复合物的结合，以确定接触和打开DNA门的关键蛋白残基。topo IV及其DNA门的进展将促进对染色体生物学的基本理解，并将有助于未来设计更有效的喹诺酮类药物。

The enzyme topo IV mediates the untangling of bacterial chromosomes prior to their segregation at cell division. Topo IV crosses one DNA helix through another allowing the separation of topologically interlocked chromosomes. It does this by an unusual mechanism: it makes a transient double-stranded DNA break (often called a 'gate') in one molecule through which the second DNA molecule is passed. Antibacterial quinolone drugs act by stabilising the open DNA gate which interferes with DNA replication causing cell death. Indeed, quinolones are now important drugs for the treatment of pneumonia and other infections caused by Streptococcus pneumoniae and othe Gram-positive pathogens. Despite it scientific interest and medical importance, little is known about the mechanism of topo IV and its drug interactions. In this study, we aim to examine (i)how S. pneumoniae topo IV recognises and opens potential gate sequences in DNA, and (ii) how quinolones stabilize such gates. The work will make use of synthetic and altered versions of a known topo IV gate which we identified on the S. pneumoniae chromosome. We shall also study the binding of mutant topo IV complexes to identify key protein residues that function to contact and open the DNA gate. Progress on topo IV and its DNA gates will advance fundamental understanding of chromosome biology and will aid the future design of more effective quinolones.