The sodium-dependentd-glucose transport protein of Helicobacter pylori
Helicobacter pylori is a Gram-negative pathogenic microaerophile with a particular tropism for the mucosal surface of the gastric epithelium. Despite its obligatory microaerophilic character, it can metabolized-glucose and/ord-galactose in both oxidative and fermentative pathways via a Na+-dependent secondary active transport, a glucokinase and enzymes of the pentose phosphate pathway. We have assigned the Na+-dependent transport of glucose to the protein product of the H. pylori 1174 gene. The gene was heterologously expressed in a glucose transport-deficient Escherichia coli strain, where transport activities of radiolabelledd-glucose,d-galactose and 2-deoxy-d-glucose were restored, consistent with the expected specificity of the hexose uptake system in H. pylori.d-Mannose was also identified as a substrate. The HP1174 transport protein was purified and reconstituted into proteoliposomes, where sodium dependence of sugar transport activity was demonstrated. Additionally the tryptophan/tyrosine fluorescence of the purified protein showed quenching by 2-deoxy-d-glucose,d-mannose,d-glucose ord-galactose in the presence of sodium ions. This is the first reported purification and characterization of an active glucose transport protein member of the TC 2.1.7 subgroup of the Major Facilitator Superfamily, constituting the route for entry of sugar nutrients into H. pylori. A model is derived of its three-dimensional structure as a paradigm of the family.
Document Type: Research Article
Affiliations: 1: Department of Chemistry, Philipps-University of Marburg, Hans-Meerwein-Strasse, 35032 Marburg, Germany. 2: The Astbury Centre for Structural Molecular Biology, Institute of Membrane and Systems Biology, University of Leeds, Leeds LS2 9JT, UK. 3: Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA.
Publication date: January 1, 2009