Recombinant mucin-type proteins carrying LacdiNAc on different O-glycan core chains fail to support H. pylori binding.

The beta 4-N-acetylgalactosaminyltransferase 3 (B4GALNT3) transfers GalNAc in a beta 1,4-linkage to GlcNAc forming the LacdiNAc (LDN) determinant on oligosaccharides. The LacdiNAc-binding adhesin (LabA) has been suggested to mediate attachment ofHelicobacter pylorito the gastric mucosaviabinding to the LDN determinant. TheO-glycan core chain specificity of B4GALNT3 is poorly defined. We investigated the specificity of B4GALNT3 on GlcNAc residues carried byO-glycan core 2, core 3 and extended core 1 precursors using transient transfection of CHO-K1 cells and a mucin-type immunoglobulin fusion protein as reporter protein. Binding of the LabA-positiveH. pyloriJ99 and 26695 strains to mucin fusion proteins carrying the LDN determinant on differentO-glycan core chains and human gastric mucins with and without LDN was assessed in a microtiter well-based binding assay, while the binding of(125)I-LDN-BSA to various clinicalH. pyloriisolates was assessed in solution. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) and western blotting confirmed the requirement of a terminal GlcNAc for B4GALNT3 activity. B4GALNT3 added a beta 1,4-linked GalNAc to GlcNAc irrespective of whether the latter was carried by a core 2, core 3 or extended core 1 chain. No LDN-mediated adhesion ofH. pyloristrains 26 695 and J99 to LDN determinants on gastric mucins or a mucin-type fusion protein carrying core 2, 3 and extended core 1O-glycans were detected in a microtiter well-based adhesion assay and no binding of a(125)I-labelled LDN-BSA neoglycoconjugate to clinicalH. pyloriisolates was identified.