Search

We solved the crystal structure of a functionally uncharacterized protein, HP0902, from Helicobacter pylori. Its structure demonstrated an all-β cupin fold that cannot bind metal ions due to the absence of a metal-binding histidine that is conserved in many metallo-cupins. In contrast, isothermal titration calorimetry and NMR titration demonstrated that HP0902 is able to bind bacterial endotoxin lipopolysaccharides (LPS) through its surface-exposed loops, where metal-binding sites are usually found in other metallo-cupins. This report constitutes the first identification of an LPS-interacting protein, both in the cupin family and in H. pylori. Furthermore, identification of the ability of HP0902 to bind LPS uncovers a putative role for this protein in H. pylori pathogenicity.

Tachyplesin I, a cationic heptadecapeptide amide containing two disulfide bonds isolated from hemocytes of Tachypleus tridentatus , which binds to lipopolysaccharide, was synthesized by a solid-phase procedure. Reduction and oxidation of the deprotected peptide amide yielded an identical peptide to native tachyplesin I in terms of chemical and biological properties. Tachyplesin 1 was found to bind to alkylphosphorylcholine accompanied by perturbation of its tyrosyl and tryptophyl residues but bound only weakly to N -acetyl-D-glucosamine tetramer.

We previously identified a novel lectin cDNA from the fall webworm [Shin et al. (1998) Insect Biochem. Mol. Biol. 28, 827–837], which encodes two carbohydrate recognition domains (CRD-N and CRD-C) and is up-regulated following bacterial challenge. The lipopolysaccharide (LPS) binding activities of the recombinant CRD-N and CRD-C (rCRD-N and rCRD-C) were investigated by enzyme-linked immunosorbent assay. The LPS binding of rCRD-N and rCRD-C was pH-dependent: at pH below 6.0, they show a higher binding ability to LPS. The binding of the rCRD-N was inhibited by both D-mannose and N-acetyl-D-glucosamine, whereas the binding of the rCRD-C was inhibited only by D-mannose. The binding of both rCRD-N and rCRD-C to Escherichia coli was mainly mediated through the O-specific chain.