Structural Studies of a Tetracycline Efflux Pump

描述（由申请人提供）：抗生素可以说是上个世纪影响人类健康的最重要的发现之一。自抗生素首次引入以来，微生物对抗生素的耐药性一直在稳步增加。四环素曾经是一种广泛使用的广谱抗菌药物，但由于编码多药耐药泵的耐药基因的活性，其有效性急剧下降。TetL属于四环素特异性转运蛋白家族，其在导致诸如肺炎、痢疾、霍乱和菌血症等疾病的大多数病原菌中占大多数抗性。详细了解四环素与TetL相互作用的分子基础以及四环素通过TetL结合和转运的机制对抗生素的未来发展将是非常宝贵的。本研究的广泛的长期研究目标是使用X射线晶体照相术获得第一个完整的图片外排转运蛋白-抗生素复合物，并表征这种相互作用的机制基础。拟议研究的具体目标如下：为了理解外排介导的四环素耐药性的基础，我建议解决TetL的结构，TetL是一种来自B.subtilis的四环素输出蛋白，单独和与抗生素结合。TetL已经结晶，并且晶体目前可结晶至4.2 A。将这些晶体改进到3 A将允许高分辨率结构测定。四环素类似物已与TetL共结晶或浸泡到TetL晶体中，这是了解这种多药耐药转运蛋白与其底物相互作用的第一步。AIM II.为了了解TetL底物特异性和四环素转运的功能基础，我建议研究预测参与底物识别和转运的残基的作用以及TetL二聚体寡聚化的意义。带电残基参与四环素结合和运输预测的路线，同源性建模，和晶体结构的TetL，将探测荧光结合实验，运输试验在重建系统，和体内活性实验。将使用平衡结合实验检查二聚体内的变构通信。 公共卫生相关性：耐药病原体是对公共卫生的全球威胁。本研究旨在证明四环素与细菌耐药泵相互作用的分子基础。了解耐药性的结构基础将为新抗生素的未来开发开辟新的领域。

DESCRIPTION (provided by applicant): Antibiotics are arguably one of the most important discoveries impacting human health in the last century. Microbial resistance to antibiotics has steadily increased since they were first introduced. Tetracycline, once a widely prescribed broad specturum antimicrobial, has seen a sharp decline in effectiveness mainly due to the activity of resistance genes encoding multi-drug resistance pumps. TetL belongs to a family of tetracycline-specific transporters that account for the majority of resistance in most pathogenic bacteria responsible for diseases such as pneumonia, dysentery, cholera, and bacteremia. Detailed information about the molecular basis of interaction and mechanism of tetracycline binding and transport through TetL will be invaluable to the future development of antibiotics. The broad long term research objectives of this study are to use x-ray crystallagraphy to obtain the first complete picture of an efflux transporter-antibiotic complex and to characterize the mechanistic basis of this interaction. The specific aims for the proposed studies are as follows: Aim I. To understand the basis of efflux mediated tetracycline resistance, I propose to solve the structure of TetL, a tetracycline exporter from B.subtilis, alone and bound to an antibiotic. TetL has been crystallized and crystals currently diffract to 4.2 A. Improvement of these crystals to 3 A will allow for high resolution structural determination. Tetracycline analogs have been co-crystallized with TetL or soaked into TetL crystals, the first steps toward understanding the interaction of this multidrug resistance transporter with its substrate. AIM II. To understand TetL substrate specificity and the functional basis of transport of tetracycline, I propose to examine the role of residues predicted to be involved in substrate recognition and transport and the significance of TetL dimeric oligomerization. Charged residues involved in tetracycline binding and transport predicted from alignments, homology modeling, and the crystal structure of TetL, will be probed with fluorescent binding experiments, transport assays in reconstituted systems, and in vivo activity experiments. Allosteric communication within the dimer will be examined using equilibrium binding experiments. PUBLIC HEALTH RELEVANCE: Drug-resistant pathogens are global threats to public health. This research seeks to demonstrate the molecular basis of a tetracycline interaction with a bacterial drug resistance pump. Understanding the structural basis of drug resistance will open the field to future development of new antibiotics.