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.
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.
|Kryshtafovych, Andriy; Moult, John; Bales, Patrick et al. (2014) Challenging the state of the art in protein structure prediction: Highlights of experimental target structures for the 10th Critical Assessment of Techniques for Protein Structure Prediction Experiment CASP10. Proteins 82 Suppl 2:26-42|
|Ozorowski, Gabriel; Milton, Saskia; Luecke, Hartmut (2013) Structure of a C-terminal AHNAK peptide in a 1:2:2 complex with S100A10 and an acetylated N-terminal peptide of annexin A2. Acta Crystallogr D Biol Crystallogr 69:92-104|
|Wassman, Christopher D; Baronio, Roberta; Demir, Ozlem et al. (2013) Computational identification of a transiently open L1/S3 pocket for reactivation of mutant p53. Nat Commun 4:1407|
|Strugatsky, David; McNulty, Reginald; Munson, Keith et al. (2013) Structure of the proton-gated urea channel from the gastric pathogen Helicobacter pylori. Nature 493:255-8|
|Scott, David R; Marcus, Elizabeth A; Wen, Yi et al. (2010) Cytoplasmic histidine kinase (HP0244)-regulated assembly of urease with UreI, a channel for urea and its metabolites, CO2, NH3, and NH4(+), is necessary for acid survival of Helicobacter pylori. J Bacteriol 192:94-103|