Probing Allosteric Inhibition and Activation of Acinetobacter baumannii ATP Phosphoribosyltransferase.

抗菌素耐药性正在上升。如果不加以妥善处理，预计到2050年，这一全球性威胁夺去的生命将超过癌症。我们迫切需要能够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致病菌。在无法诊断的急性感染病例中，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，这有利于非致病菌的耐药菌株的增殖。通过几种水平基因转移机制，赋予抗性的基因或质粒最终可能进入致病物种。在慢性或复发性感染和医院相关性感染（HAIs）的情况下，通常伴随着对导致该疾病的细菌种类的诊断，窄谱抗生素是理想的。这是因为它们只会针对这种细菌，避免了对其他细菌的选择性压力。这一策略将延长药物的（有效）寿命，保持健康的微生物群，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点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的医院病原体，其抗微生物药物耐药性菌株的增殖促使世界卫生组织将其列为需要新型抗生素的最关键细菌。它经常引起艾滋病和复发性感染，通常是肺炎。鲍曼不动杆菌分子靶点的独特鉴定将有助于开发针对该物种的有效窄谱抗生素。鲍曼不动杆菌对抗菌素产生耐药性的关键因素是其形成生物膜的能力及其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药物开发靶点。ATP磷酸核糖基转移酶（ATP phosphooribosyltransferase， ATPPRT）是一种短形式的异八聚体ATP - prt，由两种不同的蛋白质组成：HisGS（催化亚基）和HisZ（调节亚基），后者通过组氨酸结合激活HisGS的变构催化并介导其变构抑制。具体来说，在鲍曼不动杆菌中，即使在富培养基中，HisZ也被证明是生长所必需的，这表明对这种高能量消耗途径的调节至关重要。有趣的是，在富培养基中，HisGS并不是生长所必需的，但它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持续存在于肺部所必需的。因此，破坏HisZ的功能（例如，用变构激活剂）将阻止细菌生长，而抑制HisGS将防止肺炎期间在肺部持续存在。因此，本项目将采用实验和计算方法：剖析组氨酸对ATPPRT变构抑制的分子、原子和动态基础；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.