Probing Allosteric Inhibition and Activation of Acinetobacter baumannii ATP Phosphoribosyltransferase.

抗菌素耐药性正在上升。如果不妥善解决，预计到2050年，这一全球威胁夺走的生命将超过癌症。我们迫切需要能影响新分子靶点的新药。更重要的是，我们需要不同的策略来开发更有效的抗生素来对抗病原菌。在诊断缺失的急性感染病例中，广谱抗生素是必不可少的。然而，它们的缺点是对体内大多数细菌增加了不必要的选择性压力，这有利于耐药非病原菌菌株的增殖。通过水平基因转移的几种机制，赋予抗性的基因或质粒最终可能最终形成致病物种。在慢性或复发性感染和医院相关感染(HAI)的病例中，通常伴随着对导致疾病的细菌种类的诊断，窄谱抗生素是理想的。这是因为他们将只针对该物种，避免对其他细菌施加选择性压力。这一策略将延长药物的(有用)寿命，保护健康的微生物区系，并最终有助于减少抗菌素耐药性的传播。窄谱抗生素的开发需要对合适的分子靶标进行鉴定和深入的机理知识。鲍曼不动杆菌是一种革兰氏阴性医院内病原菌，其耐药菌株的激增促使世卫组织将其列为最关键的细菌，需要新的抗生素来对抗。它经常导致禽流感和反复感染，通常是肺炎。鲍曼不动杆菌独特有效的分子靶标的鉴定将有助于开发有效的窄谱抗生素来对抗该物种。鲍曼不动杆菌耐药的关键因素是其形成生物膜的能力和在肺部持续存在的能力。鲍曼不动杆菌中组氨酸生物合成的第一个酶是一个有吸引力的有效药物开发靶点。三磷酸腺苷磷酸核糖转移酶(ATPPRT)是由两种不同的蛋白质组成的短型异构体ATPPRT：HisGS是催化亚基，HisZ是调节亚基，通过组氨酸结合来激活HisGS的催化并介导其变构抑制。具体地说，在鲍曼曲霉中，HISZ已被证明即使在富含介质中也是生长所必需的，这表明对这一高耗能途径的调控至关重要。耐人寻味的是，HisGS不是在富含介质中生长所必需的，但与其他几种组氨酸生物合成酶一起，是鲍曼不动杆菌在肺炎期间在肺部持续存在所必需的。因此，破坏HISZ功能(如使用变构激活剂)将阻止细菌生长，而抑制HisGS将阻止肺炎期间肺内的持久性。因此，本项目将采用实验和计算方法：剖析组氨酸抑制ATPPRT变构的分子、原子和动力学基础；发现/开发变构激活剂ATPPRT并阐明其作用机制；发现/开发ATPPRT的变构和/或正构抑制剂并阐明其作用机制。

Antimicrobial resistance is on the rise. This global threat is predicted to claim more lives than cancer by 2050 if not properly addressed. We urgently need novel drugs that affect new molecular targets. More than that, we need different strategies to develop more effective antibiotics against pathogenic bacteria. Broad-spectrum antibiotics are indispensable in cases of acute infections where a diagnosis is missing. However, they have the disadvantage of adding undue selective pressure against most bacteria in the body, which favours the proliferation of drug-resistant strains of non-pathogenic bacteria. By several mechanisms of horizontal gene transfer, the genes or plasmids conferring resistance may, in time, end up in pathogenic species. In cases of chronic or recurrent infections and hospital-associated infections (HAIs), which are often accompanied by a diagnosis of the bacterial species responsible for the disease, narrow-spectrum antibiotics are ideal. This is because they will target only that species, avoiding selective pressure on other bacteria. This strategy will increase the (useful) lifespan of the drug, preserve the healthy microbiota, and ultimately help reduce the spread of antimicrobial resistance. The development of narrow-spectrum antibiotics requires identification and in-depth mechanistic knowledge of suitable molecular targets. Acinetobacter baumannii is a Gram-negative nosocomial pathogen whose proliferation of antimicrobial resistance strains prompted the WHO to place it as the most critical bacterium against which novel antibiotics are needed. It often causes HAIs and recurrent infections, usually pneumonia. The characterisation of uniquely validated molecular targets in A. baumannii will aid the development of efficient narrow-spectrum antibiotics against this species. The key factors responsible for antimicrobial resistance in A. baumannii are its ability to form biofilms and its capacity to persist in the lungs. The first enzyme of histidine biosynthesis in A. baumannii is an attractive validated target for drug development. ATP phosphoribosyltransferase (ATPPRT) is a short-form, hetero-octameric ATPPRT made up of two different proteins: HisGS, the catalytic subunit, and HisZ, a regulatory subunit that allosterically activates catalysis by HisGS and mediates its allosteric inhibition through histidine binding. Specifically, in A. baumannii, HisZ has been shown to be essential for growth even in rich medium, which suggests that regulation of this highly energy-consuming pathway is of paramount importance. Intriguingly, HisGS is not essential for growth in rich medium, but is required, along with several other histidine biosynthesis enzymes, for A. baumannii to persist in the lungs during pneumonia. Thus, disrupting HisZ function (e.g. with allosteric activators) will halt bacterial growth, while inhibiting HisGS will prevent persistence in the lung during pneumonia.Accordingly, this project will employ experimental and computational approaches to: Dissect the molecular, atomic, and dynamic basis for ATPPRT allosteric inhibition by histidine; Discover/develop allosteric activators ATPPRT and elucidate their mechanism of action; Discover/develop allosteric and/or orthosteric inhibitors of ATPPRT and elucidate their mechanism of action.