High-affinity binding of laminin by Helicobacter pylori: evidence for a lectin-like interaction

Laminin, the major glycoprotein of basement membranes, was shown to be bound by the human gastric pathogen Helicobacter pylori. Binding of 125I-laminin by strain 17874 was time-dependent, specific and saturable. Scatchard analysis of specific binding indicated about 2000 binding sites per cell with a dissociation constant of 8.5 pM. Treatment of the cells by heat (80 degrees) and with proteolytic enzymes drastically reduced laminin binding, suggesting that the laminin receptors are surface proteins. Some highly glycosylated glycoproteins inhibited laminin binding by 50%. Furthermore, N-acetylneuraminyllactose decreased laminin binding by 70% and neuraminidase treatment of laminin by 50%, while a recombinant B1 chain of laminin, containing high-mannose type oligosaccharides, inhibited binding by only 25%. This suggests that terminal sialic acids on laminin compete for a specific sugar binding protein(s) on H. pylori cells.