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

描述（由申请人提供）：幽门螺杆菌感染胃粘膜仍然是一个世界性问题，并导致消化性溃疡和胃癌。如果不积极干预，发达国家至少20%的人口将继续受到这种胃病原体的感染。消灭这种生物将有助于预防疾病。目前的根除需要三联疗法，质子泵抑制剂和两种抗生素，每天两次，持续10至14天。对克拉霉素或甲硝唑的耐药率> 20%，且呈上升趋势。没有单一疗法是有效的。胃感染H. pylori依赖于该病原体特有的通道UreI的表达。UreI是尿素快速进入细菌内尿素酶所必需的质子门控尿素通道，对于在胃的酸性环境中维持周质在pH 6.1（低至pH 2.5）是必需的，从而允许胃的定殖。通道的表达在胃中增加。该通道具有193个残基，具有六个跨膜区段和三个周质区。突变研究表明，UreI的质子门控是由这三个周质区域中的组氨酸和羧酸残基之间的氢键调节的。获得该通道的高分辨率三维结构是这项工作的主要目标。这将使这种蛋白质的独特的质子门控机制的理解，并将提供一个结构，其中一些已经被发现的抑制剂，可以对接和他们的结构-活性关系确定。抑制这一通道将有望产生特异性和有效的单一疗法来根除微生物，并迎来一个测试和治疗的时代，而不仅仅是治疗有症状的患者。这将为严重的上消化道疾病，特别是胃癌提供一种预防方法。公共卫生相关性幽门螺杆菌对人类胃的感染在西方和不发达国家仍然是一个尚未解决的问题。感染会使患胃癌的风险增加约20倍。目前的根除治疗是繁琐的，需要每天两次给予质子泵抑制剂和两种抗生素。质子门控尿素通道UreI的高分辨率结构将为开发抑制剂提供模板，该抑制剂将允许简单的靶向单药治疗，允许全球范围内的测试和治疗策略，以预防消化性溃疡疾病并降低胃腺癌的发病率。

DESCRIPTION (provided by applicant): 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. PUBLIC HEALTH RELEVANCE Infection of the human stomach by Helicobacter pylori remains an unresolved problem in both the West and underdeveloped countries. Infection increases the risk of developing gastric cancer about 20-fold. Current eradication therapy is cumbersome, requiring twice-a-day administration of a proton-pump inhibitor and two antibiotics. A high-resolution structure of the proton-gated urea channel, UreI, will provide a template for the development of inhibitors that will allow simple targeted monotherapy, allowing a test and treat strategy worldwide to prevent peptic ulcer disease and reduce the incidence of gastric adenocarcinoma.