Membrane-associated Activation of Cholesterol α-Glucosyltransferase, an Enzyme Responsible for Biosynthesis of Cholesteryl-α-D-Glucopyranoside in Helicobacter pylori Critical for Its Survival

Helicobacter pylori (H. pylori) is the causative pathogen underlying gastric diseases such as chronic gastritis and gastric cancer. Previously, the authors revealed that alpha 1,4-linked N-acetylglucosamine-capped O-glycan (alpha GlcNAc) found in gland mucin suppresses H. pylori growth and motility by inhibiting catalytic activity of cholesterol alpha-glucosyltransferase (CHL alpha GcT), the enzyme responsible for biosynthesis of the major cell wall component cholesteryl-alpha-D-glucopyranoside (CGL). Here, the authors developed a polyclonal antibody specific for CHL alpha GcT and then undertook quantitative ultrastructural analysis of the enzyme's localization in H. pylori. They show that 66.3% of CHL alpha GcT is detected in the cytoplasm beneath the H. pylori inner membrane, whereas 24.7% is present on the inner membrane. In addition, 2.6%, 5.0%, and 1.4% of the protein were detected in the periplasm, on the outer membrane, and outside microbes, respectively. By using an in vitro CHL alpha GcT assay with fractionated H. pylori proteins, which were used as an enzyme source for CHL alpha GcT, the authors demonstrated that the membrane fraction formed CGL, whereas other fractions did not. These data combined together indicate that CHL alpha GcT is originally synthesized in the cytoplasm of H. pylori as an inactive form and then activated when it is associated with the cell membrane. This article contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials. (J Histochem Cytochem 59:98-105, 2011)