Identification of sialyl Lewis A as a potential ligand for the Helicobacter pylori outer membrane protein HopZ

Helicobacter pylori, a gram-negative bacterium, persistently colonizes the human gastric mucosa and is implicated in the development of gastritis, ulcers, and gastric cancer. This colonization depends on specific interactions between bacterial outer membrane proteins (OMPs) and ligands present on the host cell surface. Among the well-characterized H. pylori adhesins, BabA and SabA target Lewis antigens to facilitate bacterial adhesion and immune evasion. However, the roles of other OMPs remain poorly understood. In this study, we investigated the potential glycan-binding properties of HopZ, a phase-variable OMP implicated in H. pylori adherence to gastric epithelial cells. Structural modeling using AlphaFold2 revealed that HopZ shares significant tertiary structural similarity with BabA, particularly in a crown-like region, suggesting a role in glycan recognition. We expressed and purified a recombinant HopZ extracellular domain fused to ProS2 and GST for functional analysis. Glycan array screening demonstrated that HopZ-ECD specifically binds to sialyl Lewis a (SLe^a), a fucosylated Lewis glycan structurally similar to the known BabA ligand Lewis b. However, in vitro adherence assays using SLe^a-conjugated plates did not confirm HopZ-specific bacterial binding, suggesting that the presentation and multivalency of glycans and HopZ may critically influence binding interactions. These findings provide the first direct evidence of SLe^a as a potential ligand for HopZ and underscore the need for further studies under physiologically relevant conditions.