Four Mtb Membrane Proteins: Structure and Function

描述（由申请人提供）：没有其他病原体比结核分枝杆菌造成的死亡率更高，每年有近200万人死亡。通过在各种膜模拟环境中表征膜蛋白结构的能力，可以大大提高潜在药物靶点的功能知识。膜蛋白代表了这些靶点的大部分，然而在Mtb基因组中只有1200个假定的膜蛋白中有一个被表征，只有少数其他的与密切相关物种的蛋白同源性很好地建模。我们建议在这里表征主链结构和动力学，并从结核分枝杆菌基因组中获得四种重要膜蛋白的生物学功能的机制知识。了解膜蛋白的结构和功能代表了一个重大的科学前沿，对国家和世界的健康具有深远的重要意义。在过去的几十年里，虽然有相当多的潜在药物正在开发中，但对于结核分枝杆菌没有新药。广泛耐药的结核分枝杆菌去年在南非造成53名患者中的52人死亡，现在被认为已经蔓延到非洲大陆的许多贫穷和不发达国家。此外，结核分枝杆菌的潜伏状态所必需的漫长的药物治疗方案大大复杂化了治疗。因此，了解进入和退出潜伏状态是非常重要的。许多障碍共同阻碍了膜蛋白的结构表征（蛋白质数据库中0.3%的结构与大多数基因组的30%相比）。与所有的结构方法一样，主要的挑战是样品制备。在过去的一年里，溶液核磁共振和固态核磁共振在这一领域取得了重大进展。不仅样品制备具有挑战性，而且膜蛋白具有多种构象和功能状态，使对这些蛋白质的功能理解复杂化，需要更多的结构工作。此外，它们的动态更加复杂，反映了异质环境；它们形成的复合物具有不同的分子相互作用平衡。这四种蛋白质包括CorA，其中已经有一种来自海洋热藻的晶体结构，用于这种Mg2+转运体的封闭状态。我们建议表征Mtb跨膜结构域，并建立一个Mg2+通过CorA转运的模型。对于Kdp复合物，我们将重点关注被认为在K+转运系统中具有协调作用的必需的KdpC蛋白。ChiZ被认为是细胞分裂的抑制剂，并可能成为进入潜伏状态的调节剂。Rv1861似乎是一种八聚体蛋白，可水解ATP，并可能与糖基转移酶形成复合物。

DESCRIPTION (provided by applicant): No other pathogen causes more mortality than Mycobacterium tuberculosis with nearly 2 million deaths per year. Through an ability to characterize membrane protein structure in various membrane mimetic environments, functional knowledge of potential drug targets can be greatly advanced. Membrane proteins represent the majority of these targets, yet only one out of 1200 putative membrane proteins in the Mtb genome is characterized and only a few others are well modeled by homology with proteins from closely related species. We propose here to characterize the backbone structure and dynamics and to gain mechanistic knowledge of the biological function of four significant membrane proteins from the Mtb genome. Understanding membrane protein structure and function represents a major scientific frontier that is profoundly important to the Nation's and the World's health. For M. tuberculosis there have been no new drugs in the past few decades although there are quite a few potential drugs in the pipeline. Extensively drug resistant Mtb, which killed 52 of 53 patients in South Africa last year is now thought to have spread to many poor and undeveloped countries on the African continent. Furthermore, the lengthy drug regimen necessitated by the latent state of Mtb greatly complicates treatment. Therefore, understanding entry and exit from the latent state is very important. Many obstacles have conspired to impede the structural characterization of membrane proteins (0.3% of the structures in the Protein Data Bank versus 30% of most genomes). As with all of the structural methods the primary challenge has been in sample preparation. Over the past year very significant progress has been made in this arena for solution and solid-state NMR. Not only is sample preparation challenging, but membrane proteins have multiple conformational and functional states complicating the functional understanding of these proteins and necessitating more structural work. In addition, their dynamics is more complex reflecting a heterogeneous environment; and they form complexes with a different balance of molecular interactions. These four proteins include CorA for which there is already a crystal structure from Thermatoga maritima for the closed state of this Mg2+ transporter. We propose to characterize the Mtb transmembrane domain and develop a model for Mg2+ transport by CorA. For the Kdp complex we will focus on the essential KdpC protein that is thought to have a coordinating role in this K+ transport system. ChiZ is thought to be an inhibitor of cell division and potentially a regulator of entry into the latent state. Rv1861 appears to be a octameric protein that hydrolyzes ATP and potentially forms a complex with a glycosyltransferase.