Mechanism and Spread of Qnr-Mediated Resistance

Qnr介导的耐药机制和传播

• 批准号: 6835177
• 负责人: David C Hooper
• 金额: $ 21.88万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6835177
• 关键词: DNA gyrase; DNA topoisomerases; X ray crystallography; bacterial genetics; biochemical evolution; drug resistance; molecular cloning; peptides; protein binding; protein protein interaction; protein purification; quinoline; structural biology; surface plasmon resonance

DESCRIPTION (provided by applicant): Mechanism and Spread of Qnr-Mediated Resistance. Quinolones are widely used antimicrobial agents because of their broad antibacterial spectrum, low toxicity, and reliable action against otherwise resistant pathogens. Bacterial resistance to quinolones, however, is increasing and has reached alarming levels in some parts of Europe and the Far East. Various chromosomal mutations contribute to this resistance. Plasmid-mediated resistance was long thought not to exist. We discovered a plasmid-encoded protein termed Qnr that protects DNA gyrase from quinolone inhibition. Qnr acts additively with chromosomal mechanisms for quinolone resistance, belongs to the pentapeptide repeat family of proteins and, by a gel displacement assay, binds to the gyrase tetramer as well as to the GyrA and GyrB subunits with differing affinities. Although initially found at a single hospital in the United States, the qnr gene has recently been discovered in clinical Escherichia coli isolates from the Far East and in about 10% of quinolone resistant Klebsiella pneumoniae strains from the US. The aims of this proposal are to explore the hypothesis that Qnr blocks quinolone binding to gyrase, to study Qnr binding kinetics by surface plasmon resonance, to investigate whether Qnr can also protect gyrase from such protein inhibitors as MccB17, CcdB, and Gyrl, to study further the prevalence of qnr and the genetic basis of its acquisition by plasmids, and to explore whether Qnr and an active gyrase fragment can co-crystallize for structural analysis by x-ray diffraction. These studies are important not only for understanding an emerging resistance mechanism but should also reveal details of how DNA gyrase and related topoisomerases function and how proteins in the pentapeptide family interact with and regulate the activity of other proteins.

描述（由申请人提供）：Qnr 介导的耐药性的机制和传播。喹诺酮类药物因其抗菌谱广、毒性低以及对其他耐药病原体具有可靠的作用而被广泛使用的抗菌剂。然而，细菌对喹诺酮类药物的耐药性正在增加，在欧洲和远东的一些地区已达到令人震惊的水平。多种染色体突变导致了这种耐药性。长期以来，人们一直认为质粒介导的耐药性不存在。我们发现了一种名为 Qnr 的质粒编码蛋白，它可以保护 DNA 旋转酶免受喹诺酮的抑制。 Qnr 与喹诺酮耐药性的染色体机制相加，属于蛋白质五肽重复家族，通过凝胶置换测定，以不同的亲和力与旋转酶四聚体以及 GyrA 和 GyrB 亚基结合。虽然qnr基因最初是在美国的一家医院发现的，但最近在来自远东的临床大肠杆菌分离株和来自美国的约10%的喹诺酮耐药肺炎克雷伯菌菌株中发现了qnr基因。本提案的目的是探索 Qnr 阻断喹诺酮与旋转酶结合的假设，通过表面等离振子共振研究 Qnr 结合动力学，研究 Qnr 是否也可以保护旋转酶免受 McB17、CcdB 和 Gyrl 等蛋白质抑制剂的影响，以研究进一步了解qnr的流行及其通过质粒获得的遗传基础，并探讨Qnr和活性旋转酶片段是否可以共结晶以进行结构分析X射线衍射。这些研究不仅对于理解新出现的耐药机制很重要，而且还应该揭示DNA旋转酶和相关拓扑异构酶如何发挥作用以及五肽家族中的蛋白质如何与其他蛋白质相互作用并调节其他蛋白质的活性的细节。