Molecular grammar of SurA-client interactions in the periplasm of gram-negative bacteria

据世界卫生组织称，预计到2050年，抗生素耐药性每年将导致1000万人死亡，革兰氏阴性病原体占对人类健康构成最大威胁的12种细菌中的9种。这些革兰氏阴性病原体具有独特的外膜（OM），作为抵御潜在有害分子（如抗生素）攻击的第一道防线。因此，OM对细菌的生存至关重要，也是某些细菌对不同类型的抗生素产生耐药性的原因之一。因此，找到阻止OM正确组装的方法可能会产生杀死革兰氏阴性菌的新途径，或者使它们对现有抗生素更敏感。然而，通过OM构建的机制仍然是神秘的，这使得其组装难以靶向治疗。在这里，我们建议确定OM的关键蛋白质-所谓的外膜蛋白（或OMPs） -如何折叠到OM中以创建通常不可穿透的细胞壁。omp在细菌的毒力和生存中起着至关重要的作用，因此，通过了解omp如何组装到OM中，有可能开发针对这一重要过程的新药。参与确保omp到达OM的关键蛋白质是一种称为SurA的伴侣蛋白。SurA是开发控制革兰氏阴性病原体新药的一个有吸引力的靶点，因为扰乱SurA的伴侣功能会导致细菌活力和毒力的丧失以及对抗生素的敏感性增加。然而，为了靶向SurA的伴侣功能，还需要进一步的工作来了解其作用机制。我们最近发现，SurA上的两个关键位点负责识别omp。这是令人兴奋的，因为它表明这些位点中的一个或两个都可以成为新的类药物分子的良好靶标。然而，我们仍然不了解这两个结合位点如何参与OMP结合和伴侣功能。在这里，我们建议使用来自一系列互补和尖端实验方法的信息（包括核磁共振波谱，质谱，单分子福斯特共振能量转移，生物化学/生物物理学和生物信息学）来了解SurA上每个新发现的OMP结合位点如何识别其OMP客户端的特定信号。此外，我们建议确定这两个结合位点如何共同作用以实现其伴侣功能，特别是关于SurA在保护新合成的omp不聚集和促进其递送到OM中的作用。这将揭示SurA的分子特征，这些特征对于协助OMP的生物发生至关重要，未来可能会导致开发急需的抗生素的新策略，这些抗生素针对威胁人类、植物和动物的革兰氏阴性病原体。

Antibiotic resistance is projected to cause 10 million deaths per year by 2050, with gram-negative pathogens comprising 9 of the 12 bacteria that pose the greatest threat to human health, according to the World Health Organisation. These gram-negative pathogens have a unique outer membrane (OM) that acts as a first line of defence against an assault from potentially harmful molecules to the bacteria, such as antibiotics. As a result, the OM is essential for bacterial survival and is one reason why certain bacteria are resistant to different types of antibiotics. Finding ways to prevent correct assembly of the OM may therefore produce new routes to kill gram-negative bacteria, or make them more susceptible to existing antibiotics. However, the mechanism by with the OM is built remains mysterious, making its assembly difficult to target with therapeutics.Here we propose to determine how key proteins of the OM - so-called outer membrane proteins (or OMPs) - are folded into the OM to create the usually impenetrable cell wall. OMPs play essential roles in bacterial virulence and survival, so by understanding how OMPs are assembled into the OM it may be possible to develop new drugs that target this essential process. A key protein involved in ensuring OMPs reach the OM is a chaperone protein called SurA. SurA is an attractive target for the development of new drugs to control gram-negative pathogens because perturbing the chaperone function of SurA results in a loss of bacterial viability and virulence along with increased sensitivity to antibiotics. However, in order to target the chaperone function of SurA, further work is needed to understand its mechanism of action. We have recently discovered that two key sites on SurA are responsible for recognising OMPs. This is exciting, as it suggests that one or both of these sites could make good targets for new drug-like molecules. However, we still do not understand how each of these two binding sites contribute to OMP binding and chaperone function. Here we propose to use information from an array of complementary and cutting-edge experimental methodologies (including NMR spectroscopy, mass spectrometry, single molecular Forster resonance energy transfer, biochemistry/biophysics and bioinformatics) to understand how each of the newly discovered OMP binding sites on SurA recognises specific signals within its OMP clients. Further, we propose to determine how these two binding sites work together to bring about its chaperone function, in particular regarding SurA's role in protecting newly synthesised OMPs from aggregation and facilitating their delivery to the OM. This will uncover the molecular features of SurA that are essential for assisting in OMP biogenesis, which, in the future, could lead to new strategies to develop much-needed antibiotics that target gram-negative pathogens that threaten humans, plants and animals.