Molecular dissection of a novel protein-protein interaction: structure and mechanism of the staphylococcal fusidic acid-resistance protein FusB

细菌对抗生素的耐药性是一个日益严重的问题，因为它干扰了我们成功治疗细菌感染的能力。为了保持现有抗生素的活性，并指导开发不易产生耐药性的新抗生素，详细了解细菌产生这种耐药性的机制将是至关重要的。福西地酸是一种重要的抗生素，用于治疗由“超级细菌”金黄色葡萄球菌引起的细菌感染。这种药物通过干扰一种叫做伸长因子g （EF-G）的蛋白质的功能来起作用，这种蛋白质帮助细菌制造蛋白质。然而，越来越多的金黄色葡萄球菌菌株对这种药物产生耐药性，因为它们产生一种叫做FusB的蛋白质，这种蛋白质与EF-G结合，保护它免受抗生素的影响。我们实验室最近的工作表明，这种FusB耐药机制非常不寻常，与迄今为止表征的大多数其他抗生素耐药机制不同。此外，FusB蛋白似乎不仅具有保护细胞免受fususidic酸侵害的功能，而且还在细胞蛋白质制造中起辅助作用。因此，它具有重要的基础科学意义。FusB发挥其天然作用并引起对夫西地酸的抗性的机制仍然知之甚少。为了更好地理解FusB是如何实现这一目标的，我们的目标是利用一种称为核磁共振（NMR）波谱的技术，解决FusB蛋白单独和与EF-G蛋白结合时的3-D结构。结合实验详细检查这些蛋白质如何结合在一起，这些研究将为FusB及其执行其生物学作用的机制提供重要见解。这一信息可能使我们能够设计出阻断细菌细胞中FusB活性的方法，并克服金黄色葡萄球菌对夫西地酸的抗性。

Resistance to antibiotics among bacteria is an ever-growing problem, since it interferes with our ability to successfully treat bacterial infections. In order to preserve the activity of existing antibiotics, and to guide the development of new antibiotics which are less resistance-prone, it will be essential to understand in detail the mechanisms by which bacteria develop such resistance. Fusidic acid is an important antibiotic for the treatment of bacterial infections caused by the 'superbug', Staphylococcus aureus. The drug works by interfering with the function of a protein known as elongation factor-G (EF-G) that helps the bacterium make proteins. However, an increasing number of strains of S. aureus are becoming resistant to this drug because they produce a protein called FusB that binds to EF-G and protects it from the antibiotic. Recent work in our laboratory suggests that this FusB resistance mechanism is highly unusual, and unlike most other antibiotic resistance mechanisms characterized to date. Furthermore, it appears that the FusB protein not only functions to protect the cell from fusidic acid, but also performs an accessory role in the cellular manufacture of proteins. Consequently, it is of significant fundamental scientific interest. The mechanism by which FusB performs its native role and causes resistance to fusidic acid remain poorly understood. To better understand how FusB achieves this, we aim to solve the 3-D structure of the FusB protein, alone and when bound to the EF-G protein, using a technique known as Nuclear Magnetic Resonance (NMR) spectroscopy. In conjunction with experiments to examine in detail how these proteins bind together, these studies will provide significant insights into FusB and the mechanism by which it carries out its biological role(s). This information may allow us to devise approaches for blocking the activity of FusB in bacterial cells, and overcoming resistance to fusidic acid in S. aureus.