Helicobacter pylori infects over half the world's population, but only 3% of those infected develop peptic ulcer, gastric cancer, and mucosa-associated lymphoid tissue (MALT) lymphoma. In H. pylori, alpha-glucosyl cholesterol constitutes more than 25% of cell wall lipids, and it has been suggested that alpha-glucosyl cholesterol is essential for H. pylori viability. Here, we identified cholesterol alpha-glucosyltransferase (CHL alpha GcT) using an expression cloning strategy and showed that this enzyme is distinctively inhibited by mucin-type O-glycans similar to those present in deeper portions of the gastric mucosa. Moreover, inactivation of CHL alpha GcT by homologous recombination led to H. pylori lethality. These results indicate that H. pylori CHL alpha GcT is a unique enzyme targeted by a natural antibiotic mucin and constitutes an excellent therapeutic target to prevent H. pylori-induced peptic ulcer, gastric carcinoma, and MALT lymphoma. (c) 2006 Elsevier Inc. All rights reserved.