Hygromycin A: Activity, Biosynthesis, Export, Resistance and Regulation

描述(申请人提供)：许多临床上重要的抗生素类别，包括大环内酯类(阿奇霉素、泰利霉素)、四环素类、氨基糖苷类(庆大霉素)和新近的恶唑烷酮类(利奈唑胺)针对细菌核糖体，这是细胞内蛋白质合成所必需的。使用这些和其他抗生素对抗病原微生物不可避免地会导致细菌耐药性的发展，这在临床环境中是一个日益严重的问题。因此，继续需要开发新的抗生素，以有效地对抗多重耐药细菌，并需要能够延缓不可避免的对这些细菌的耐药性发展的方法。核糖体是开发新抗生素的最丰富和最有效的靶点之一。这种药物开发工作可以建立在分子水平上，了解核糖体与化学结构不同的结构的相互作用，生物活性(包括细胞摄取)的其他方面的结构要求，以及产生耐药性的可能机制。潮霉素A(HygA)是从吸水链霉菌中分离出来的一种抗生素，对革兰氏阳性和革兰氏阴性细菌都有活性，其作用机制涉及到与核糖体的独特而神秘的结合。HygA还具有与其他针对核糖体的抗生素显着不同的化学结构。出于这些原因，HygA有可能发展成为一类新的临床有用的抗生素。该项目的长期目标是全面了解潮霉素A(HygA)的活性、生物合成、出口、抗性和调节(ABERR)。这个项目期有5个具体目标，将采用多学科交叉和合作的方法，通过遗传、生物化学和结构研究来实现。目的1.详细了解HygA生物合成过程中关键步骤和新步骤的酶学。目的2.阐明HygA作为生物合成途径的中间产物和分流产物是如何与核糖体结合的。目的3.确定最终产物HygA从细胞中排泄的机制。目的4.评价抗生素和吸水链霉菌核糖体的共价修饰在提高对HygA及其相关生物合成产物的抗性中的相对作用。目标5.确定HygA ABERR过程是如何管理的，以及它们在多大程度上是协调的。 与公共卫生相关：继续需要对多重耐药细菌有效的新抗生素，并需要能够延缓对这些细菌不可避免的耐药性发展的方法。放线菌是土壤细菌，既是临床上用于治疗细菌感染的大多数抗生素的来源，也是对这些抗生素的耐药性机制的储存库。这项研究将评估与天然产物潮霉素A和相关化合物相关的生物活性和耐药机制，并最终可能导致治疗细菌感染的新疗法。

DESCRIPTION (provided by applicant): Many clinically important classes of antibiotics, including macrolides (azithromycin, telithromycin), tetracyclines, aminoglycosides (gentamycin), and more recently oxazolidinones (linezolid) target the bacterial ribosome, which is essential for intracellular protein synthesis. Use of these and other antibiotics against pathogenic microorganisms inevitably leads to development of bacterial resistance, an increasing problem within the clinical setting. There is thus a continued need to develop new antibiotics, effective against multi-drug resistant bacteria, and for approaches which can retard the inevitable development of resistance to these. The ribosome represents one of the richest and most effective targets for development of new antibiotics. Such drug development efforts can build upon a molecular level understanding of the ribosomal interactions with chemically distinct architectures, structural requirements for other aspects of biologically activity (including cellular uptake) and likely mechanisms for development of resistance. Hygromycin A (HygA), an antibiotic isolated from Streptomyces hygroscopicus and is active against both Gram-positive and Gram-negative bacteria and a mechanism of action which involves a distinct but enigmatic binding to the ribosome. HygA also has a chemical architecture which differs significantly from other antibiotics which target the ribosome. For these reasons HygA is of interest for potential development into new class of clinically-useful antibiotics. The long term project objective is to build a comprehensive understanding of hygromycin A (HygA) activity, biosynthesis, export, resistance and regulation (ABERR). This project period has 5 specific aims which will be pursed using a multi-interdisciplinary and collaborative approach with genetic, biochemical and structural studies. Aim 1. Obtain a detailed understanding of the enzymology of key and novel steps in the HygA biosynthetic process. Aim 2. Elucidate how HygA, biosynthetic pathway intermediates and shunt products, bind to ribosomes. Aim 3. Determine mechanisms by which the final product HygA is excreted from the cell. Aim 4. Evaluate the relative roles of covalent modification of both the antibiotic and the S. hygroscopicus ribosome in conferring resistance to HygA and related biosynthetic products. Aim 5. Determine how HygA ABERR processes are regulated, and to what extent are they coordinated. PUBLIC HEALTH RELEVANCE: There is continued need for new antibiotics effective against multi-drug resistant bacteria, and for approaches which can retard the inevitable development of resistance to these. Actinomycetes are soil bacteria and serve both as a source for the majority of antibiotics used clinically to treat bacterial infections and a repository for resistance mechanisms to these. This study will evaluate biological activity and resistance mechanisms associated with the natural product hygromycin A and related compounds and may ultimately lead to new therapies for treatment of bacterial infections.