Structural characterization of MCE mediated lipid transport across the Mycobacterial cell envelope

项目总结/摘要： 结核分枝杆菌（Mtb）的细胞包膜在预防结核病中起着重要的作用。 常见的抗菌剂和宿主细胞防御，而且也是Mtb必须运输宿主的屏障 衍生营养素。MCE蛋白家族（最初涉及哺乳动物细胞进入）在哺乳动物中几乎无处不在。 双膜细菌和MCE蛋白现在被认为是作为转运蛋白，促进脂质 内外膜之间的运动。虽然Mtb MCE蛋白对毒力至关重要，但它们的 结核病的发病机制尚不清楚。由于Mtb独特的细胞包膜，Mtb MCE蛋白可能采用独特的 建筑来调节交通。此外，在结核分枝杆菌感染的整个过程中，MCE转运蛋白 据信由MCE转录调节因子（MCeR）差异表达。这表明 分枝杆菌中的环境感知反过来改变了mce操纵子的转录。利用结构生物学， 生物化学和遗传互补分析，我将提供第一次瞥见结核分枝杆菌的结构 Mce蛋白系统，并阐明如何在分子水平上与它们的操纵基因序列相互作用， 调节MCE操纵子。为此，我提出了以下目标：（目标1）确定Mce 4脂质的结构 来自耻垢分枝杆菌的转运系统和（目的2）结构表征和DNA结合 MCeR的特异性。我的工作将提供第一次瞥见的建筑M。黑霉素Mce 4 转运系统，以及MceR介导的mce操纵子调控的分子机制， 可能揭示结核分枝杆菌细胞包膜维持的机制，并提供一个新的靶点， 治疗学

PROJECT SUMMARY / ABSTRACT: The cell envelope of Mycobacterium tuberculosis (Mtb) serves an important role as protection against common antimicrobials and host cell defenses, but also a barrier through which Mtb must transport host derived nutrients. The MCE protein family (originally implicated in Mammalian Cell Entry) is nearly ubiquitous in double-membraned bacteria, and MCE proteins are now believed to act as transporters that facilitate lipid movement between the inner and outer membranes. While Mtb MCE proteins are critical for virulence, their mechanism in Mtb remains unclear. Due to Mtb’s distinct cell envelope Mtb MCE proteins likely adopt a unique architecture to mediate transport. In addition, throughout the course of Mtb infection MCE transporters are believed to be differentially expressed by MCE transcriptional regulators (MceRs). This suggests that environmental sensing in Mycobacteria in turn alters transcription of the mce operons. Using structural biology, biochemistry, and genetic complementation assays, I will provide the first glimpse into the architecture of Mtb Mce protein systems and elucidate how MceRs interact with their operator sequences at the molecular level to regulate mce operons. To do so I propose the following aims: (Aim 1) structure determination of the Mce4 lipid transport system from Mycobacterium smegmatis and (Aim 2) structural characterization and DNA-binding specificity of MceRs. My work will provide the first glimpse at the architecture of the M. smegmatis Mce4 transporter system, as well as the molecular mechanisms of MceR mediated mce operon regulation, which may shed light on the mechanisms of cell envelope maintenance in Mtb and provide a novel target for therapeutics.