Unravelling the Bam complex

微生物对抗生素等抗菌疗法的耐药性日益增长，这是一个重大的全球公共卫生问题。目前估计，仅在欧洲，每年就有25000人死亡，约250万天的住院天数可以避免，每年的经济负担估计至少为12亿GB。革兰氏阴性细菌的耐药性最严重，基本上几乎没有正在开发或可能在不久的将来投入临床使用的抗生素。政府首席医疗官Dame Sally Davies教授在最近的一份报告中将其比作一枚定时炸弹，并警告说，如果我们失去对抗感染的能力，常规手术可能在短短20年内变得致命。对革兰氏阴性细菌细胞膜的了解对于开发新的抗菌剂至关重要。所有的革兰氏阴性细菌都有两层包围细胞的膜，由一个被称为周质的空间隔开。这两层膜的外层特别能抵抗小分子的渗透。这种膜的主要功能是形成一个半透层，保护细菌免受环境的影响，但也控制分子进出细胞的运动，以及细胞如何与环境相互作用。正是这种膜内的蛋白质通过提供基本的生理、致病和耐药功能来控制这些机制，因此是微生物战争的工具，因为它们介导了许多导致感染和疾病进展的致命过程。识别可以防止这种膜形成的化合物可能会导致下一代抗菌剂的开发。最近，一种称为Bam复合体的单一蛋白质复合体被发现负责将大部分蛋白质折叠并插入外膜，因此被认为是形成外膜的关键瓶颈。因此，了解这种复合体的工作原理是至关重要的，因为设计抑制这一过程的化合物将抑制外膜蛋白的生物发生，从而抑制外膜蛋白的基本生理、致病和耐药性功能，并可能被证明有助于对抗各种革兰氏阴性病原体。在这个研究项目中，我们计划表征Bam复合体进行的机制过程，以便将蛋白质折叠到外膜，我们将识别在外膜蛋白插入过程中形成的配体相互作用部位和结合口袋，从而提供有价值的机制见解，这将有助于发现分子抑制剂和新型抗菌剂。

The growing resistance of micro-organisms to antimicrobial therapies, such as antibiotics, is a significant global public health issue. In Europe alone this is currently estimated to result in an additional 25,000 deaths each year, approximately 2.5 million avoidable days in hospital and an economic burden estimated to be at least £1.2 Billion per year. Resistance is most serious for Gram-negative bacteria, with essentially few antibiotics under development or likely to be available for clinical use in the near future. A recent report by Professor Dame Sally Davies, the Government's Chief Medical Officer, likened it to a 'ticking time bomb' and warned that routine operations could become deadly in just 20 years if we lose the ability to fight infection.The understanding of the Gram-negative bacterial cell envelope is critical to developing new antimicrobial agents. All Gram-negative bacteria possess two membranes that enclose the cell, separated by a space known as the periplasm. The outer of the two membranes is particularly resistant to the penetration of small molecules. The main function of this membrane is to form a semi-permeable layer that protects the bacterium from the environment but also to control the movement of molecules into and out of the cell and how the cell interacts with its environment. It is the proteins within this membrane that control these mechanisms by providing essential physiological, pathogenic and drug resistance functions and hence are the instruments of microbial warfare as they mediate many of the lethal processes responsible for infection and disease progression. Identifying compounds that can prevent the formation of this membrane could lead to the development of the next generation of antimicrobials. Recently a single protein complex called the Bam complex was identified as being responsible for the folding and insertion of most if not all of the proteins into the outer membrane and hence has been identified as a key bottleneck in the formation of this membrane. Understanding how this complex works is therefore critical as the design of compounds that inhibit this process would inhibit outer membrane protein biogenesis and therefore essential physiological, pathogenic and drug resistance functions and could prove useful in combating diverse Gram-negative pathogens.In this research project we plan to characterise the mechanistic processes the Bam complex undertakes in order to fold proteins into the outer membrane, we will identify ligand interaction sites and binding pockets that form during outer membrane protein insertion and thus provide valuable mechanistic insights that will aid in the discovery of molecular inhibitors and new classes of antimicrobial agents.