Key Laboratory of Zoonosis, Ministry of Education, Institute of Zoonosis, College of Veterinary Medicine, Jilin University, Changchun, China.
PLoS One. 2013 Nov 27;8(11):e80197. doi: 10.1371/journal.pone.0080197. eCollection 2013.
α-Hemolysin (α-HL) is a self-assembling, channel-forming toxin that is produced as a soluble monomer by Staphylococcus aureus strains. Until now, α-HL has been a significant virulence target for the treatment of S. aureus infection. In our previous report, we demonstrated that some natural compounds could bind to α-HL. Due to the binding of those compounds, the conformational transition of α-HL from the monomer to the oligomer was blocked, which resulted in inhibition of the hemolytic activity of α-HL. However, these results have not indicated how the binding of the α-HL inhibitors influence the conformational transition of the whole protein during the oligomerization process. In this study, we found that three natural compounds, Oroxylin A 7-O-glucuronide (OLG), Oroxin A (ORA), and Oroxin B (ORB), when inhibiting the hemolytic activity of α-HL, could bind to the "stem" region of α-HL. This was completed using conventional Molecular Dynamics (MD) simulations. By interacting with the novel binding sites of α-HL, the ligands could form strong interactions with both sides of the binding cavity. The results of the principal component analysis (PCA) indicated that because of the inhibitors that bind to the "stem" region of α-HL, the conformational transition of α-HL from the monomer to the oligomer was restricted. This caused the inhibition of the hemolytic activity of α-HL. This novel inhibition mechanism has been confirmed by both the steered MD simulations and the experimental data obtained from a deoxycholate-induced oligomerization assay. This study can facilitate the design of new antibacterial drugs against S. aureus.
α-溶血素 (α-HL) 是一种自组装的通道形成毒素，由金黄色葡萄球菌菌株作为可溶性单体产生。到目前为止，α-HL 一直是治疗金黄色葡萄球菌感染的重要毒力靶点。在我们之前的报告中，我们证明了一些天然化合物可以与 α-HL 结合。由于这些化合物的结合，α-HL 从单体到寡聚体的构象转变被阻断，从而抑制了 α-HL 的溶血活性。然而，这些结果并没有表明 α-HL 抑制剂的结合如何影响寡聚化过程中整个蛋白质的构象转变。在这项研究中，我们发现三种天然化合物，即 7-O-葡萄糖醛酸橙皮苷（OLG）、橙皮素 A（ORA）和橙皮素 B（ORB），在抑制 α-HL 的溶血活性时，可以与 α-HL 的“茎”区结合。这是通过常规分子动力学（MD）模拟完成的。通过与 α-HL 的新结合位点相互作用，配体可以在结合腔的两侧形成强相互作用。主成分分析（PCA）的结果表明，由于抑制剂与 α-HL 的“茎”区结合，α-HL 从单体到寡聚体的构象转变受到限制。这导致了 α-HL 溶血活性的抑制。这种新的抑制机制已经通过定向 MD 模拟和去氧胆酸盐诱导的寡聚化测定获得的实验数据得到了证实。这项研究可以促进针对金黄色葡萄球菌的新型抗菌药物的设计。
