Investigation of surface-exposed proteins of the gastric bacterium Helicobacter pylori

Abstract

Colonization of the human stomach with Helicobacter pylori is a risk factor for development of gastric cancer and peptic ulcer disease. Proteins present on the surface of H. pylori mediate adhesion to the host gastric epithelium and are potentially involved in the development of adverse clinical outcomes. Relatively little is known about constituents of the H. pylori surface-exposed proteome. By using on-cell biotinylation and subcellular fractionation methods coupled with mass spectrometry analysis, I identified proteins that met multiple criteria for surface localization. A subset of surface-exposed proteins was highly susceptible to proteolysis when intact bacteria were treated with proteinase K, suggesting the presence of large surface-exposed domains. The surface topology of proteins was mapped by analyzing patterns of protease susceptibility or by use of on-cell immunolabeling. In further studies, I identified surface-exposed proteins that change in abundance in response to high environmental salt concentrations, a condition that mimics a high salt diet, which is associated with an increased risk of gastric cancer. These studies provide new insights into the repertoire of surface-exposed H. pylori proteins under multiple conditions, as well as the cell surface topology of these proteins.