Modulation of antibiotic resistance and protein synthesis by disrupting Elongation Factor G dynamics

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Antibiotic resistance is a serious public health concern; the Chief Medical Officer for England warned it poses a 'catastrophic threat' on a par with climate change or terrorism and deaths related to antibiotic resistance are predicted to outnumber those from cancer by 2050. Without concerted efforts, we face a future in which routinely treatable infections may become fatal due to a lack of effective antibiotic treatments. As few new antibiotics are becoming available it is important to overcome resistance to existing antibiotics to extend the usefulness of these important treatments. To do this we must understand how the proteins involved mediate resistance. This work aims to understand the mechanism of resistance to an important clinical antibiotic, fusidic acid (FA), and identify key regions of the proteins involved that control how they act. This could provide resources for the development of drugs to overcome this resistance and rejuvenate the usefulness of this important antibiotic.FA is used against infections by the bacteria Staphylococcus aureus and is one of few remaining oral antibiotics active against the hospital 'superbug' MRSA. FA interacts with a protein called EF-G (an important part of the machinery for making proteins) and prevents it from working, meaning bacteria cannot make proteins and so cannot grow. Resistance to FA has increased dramatically in recent years either by the interaction of another protein, FusB, with EF-G that rescues it from the effects of FA, or mutations in EF-G itself. The interaction between FusB and EF-G has recently been studied, showing FusB causes long-range changes in EF-G that produce motions in EF-G important for causing FA resistance. I have new data showing that I can disrupt these motions by altering EF-G and that when I do, the proteins become less resistant to FA. I aim to determine which parts of EF-G are important in controlling these motions to try to find key areas of EF-G that could act as targets for the development of drugs that can stop FA resistance and so extend the usefulness of this antibiotic. I will make a series of changes to EF-G and monitor the effects of those changes using structural investigations of motions in EF-G by a technique called nuclear magnetic resonance (NMR). I will then study what effects these changes have on the ability of FusB to cause FA resistance, identifying important areas of EF-G that control its response to FusB. I will use knowledge of these important areas to see if changing them in EF-G that is already resistant to FA without needing FusB can prevent it from producing FA resistance too, suggesting any areas that might control both types of resistance. To complement this, I will study whether similar motions in EF-G are important in the function of EF-G in making proteins within bacteria to try to get a better understanding of how this protein works. This could provide further information for drug discovery studies to try to stop this essential protein from working, providing a potential target for antibiotic development studies. These studies will allow us to understand how bacteria become resistant to this important antibiotic, providing information that can be used to design new antibiotic treatments to bypass this resistance. They also help us to understand the role of EF-G in the essential process of making proteins, which may show more potential drug targets for development of new antibiotics.With the increase in antibiotic resistance and few new antibiotics being discovered, it is important to use knowledge of current resistance mechanisms to develop drugs that bypass resistance or to design drugs that can be added to antibiotics to overcome the resistance. Understanding the structural basis of antibiotic resistance can lead to the development of such drugs that can be administered with the antibiotic to overcome the existing resistance, allowing us to continue to use the antibiotic to treat infections.