Four Mtb Membrane Proteins: Structure and Function

描述(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。通过在不同的膜模拟环境中表征膜蛋白结构的能力，潜在药物靶点的功能知识可以大大提高。膜蛋白代表了这些靶标中的大多数，然而在Mtb基因组中的1200个推定的膜蛋白中只有一个得到了表征，只有少数其他蛋白与来自密切相关物种的蛋白进行了很好的同源性建模。在此，我们建议对结核分枝杆菌基因组中四种重要的膜蛋白的骨架结构和动力学特征进行表征，并获得其生物学功能的机制知识。了解膜蛋白的结构和功能是一个重大的科学前沿，对国家和世界的健康都具有深远的意义。对于结核分枝杆菌，在过去的几十年里没有新的药物，尽管有相当多的潜在药物正在酝酿中。广泛耐药的结核分枝杆菌去年在南非导致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，结核分枝杆菌潜伏状态所需的冗长药物治疗方案极大地增加了治疗的复杂性。因此，从潜态中理解进出是非常重要的。许多障碍共同阻碍了膜蛋白的结构特征(蛋白质数据库中0.3%的结构，而大多数基因组的结构为30%)。与所有结构方法一样，主要的挑战是样品的制备。在过去的一年里，在溶液和固态核磁共振领域取得了非常重大的进展。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，使这些蛋白质的功能理解复杂化，并需要更多的结构工作。此外，它们的动力学更复杂，反映了不同的环境；它们形成了具有不同分子相互作用平衡的络合物。这四种蛋白质包括CorA，对于CorA，已经有来自Thermatoga maritima的晶体结构，用于该镁离子转运体的关闭状态。我们建议对Mtb跨膜结构域进行表征，并建立一个通过CORA转运镁离子的模型。对于KDP复合体，我们将重点研究被认为在这个K+转运系统中起协调作用的基本KdpC蛋白。Chiz被认为是细胞分裂的抑制者，也是进入潜伏期的潜在调节者。Rv1861似乎是一种八聚体蛋白，它能水解三磷酸腺苷，并可能与糖基转移酶形成复合体。

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.