Isolation of Helicobacter pylori Urease
Nujhat N. Ali
Mentors: Eric R. Samuels, Bradley Wallentine, Hartmut Luecke
Helicobacter pylori is a Gram-negative bacterium linked to the development of peptic ulcer disease and gastritis.
Furthermore, chronic H. pylori infection can lead to gastric cancer, the second leading cause of cancer-related
deaths worldwide. The pathogen H. pylori requires both urease and the urea channel UreI for survival in the
acidic environment of the stomach. These proteins work together to help the bacterium maintain a nearly
neutral periplasmic pH, perhaps by forming a complex with each other. Therefore, both urease and UreI are
prime targets for combating H. pylori infection. To help with the development of urease inhibitors, the
structure of urease will be determined at a higher resolution than previously available (3.00 Å) through X-ray
crystallography. Moreover, a high-resolution structure of any potential urease-UreI complex will be
determined by cryo-electron microscopy. The current focus of this project is to optimize urease expression
and purification in preparation for these experiments. Recombinant urease was expressed in Escherichia coli
BL21DE3, a well-known optimized protein-expression bacterial strain. Urease was then purified using a series
of chromatographic techniques, including hydrophobic interaction, size exclusion, and ion exchange. An
assay for testing urease activity has also been optimized and will be useful in a high-throughput screen for
urease inhibitors. Ultimately, this information may help with structure-based drug discovery, leading to more
targeted treatments for eradication of H. pylori.