Structure-Function Studies of the Proton-Gated Urea Channel from H. Pylori

项目摘要 幽门螺杆菌感染胃粘膜仍然是一个世界性的问题， 导致消化性溃疡疾病和胃癌。如果没有积极的干预，至少有20% 发达国家的人口中将继续感染这种胃部病原体。 根除这种生物将有助于预防疾病。当前的根除 需要三联疗法，一种质子泵抑制剂和两种抗生素，每天两次，每次10到 14天。克拉霉素或甲硝唑的耐药率为20%，而且还在上升。不是 单一疗法是有效的。幽门螺杆菌的胃部感染依赖于一种渠道的表达 这种病原体是UreI所特有的。UreI是一种质子门控尿素通道，是快速进入 尿素转化为细菌内尿素酶，是在酸性条件下维持周质pH 6.1所必需的 低至PH2.5的胃部环境，从而使胃部得以定植。 该通道在胃中的表达增加。该通道有193个残基，其中6个残基 跨膜段和三个周质区域。诱变研究表明， 组氨酸和羧酸之间的氢键调节UreI的质子门控 这三个周质体内的酸性残留物。获得高分辨率的3维 这条航道的结构是这项工作的主要目标。这将使我们能够理解 这种蛋白质独特的质子门控机制，并将提供一种结构， 其中一些已经被发现，可以对接，它们的结构-活性 关系已确定。对这一渠道的抑制预计会导致特定和 有效的单一疗法根除微生物并开启检测和治疗的时代，而不是 而不仅仅是治疗有症状的病人。这将为严重的 上消化道疾病，尤指胃癌。

Project Summary Infection of the gastric mucosa by Helicobacter pylori remains a worldwide problem and contributes to peptic ulcer disease and gastric cancer. Without active intervention, at least 20% of the population of developed countries will continue to be infected by this gastric pathogen. Eradication of the organism would contribute to prevention of disease. Current eradication requires triple therapy, a proton-pump inhibitor and two antibiotics given twice a day for 10 to 14 days. Resistance to either clarithromycin or metronidazole is > 20% and rising. No monotherapy is effective. Gastric infection by H. pylori depends on the expression of a channel unique to this pathogen, UreI. UreI is a proton-gated urea channel necessary for rapid access of urea to intrabacterial urease, essential for maintaining the periplasm at pH 6.1 in the acidic environment of the stomach, as low as pH 2.5, thus allowing colonization of the stomach. Expression of the channel is increased in the stomach. The channel has 193 residues with six transmembrane segments and three periplasmic regions. Mutagenesis studies have shown that the proton gating of UreI is regulated by hydrogen bonding between histidines and carboxylic acid residues in these three periplasmic regions. Obtaining a high-resolution 3-dimensional structure of this channel is the major goal of this work. This will enable understanding of the unique proton-gating mechanism of this protein and will provide a structure to which inhibitors, some of which have been discovered already, can be docked and their structure-activity relationship identified. Inhibition of this channel would be expected to result in specific and effective monotherapy for eradication of the organism and usher in an era of test and treat, rather than only treating symptomatic patients. This would provide a preventive approach to serious upper gastro-intestinal diseases, particularly gastric cancer.