Binding of vitronectin and plasminogen to Helicobacter pylori

We have studied how some extracellular matrix proteins, fibronectin, fibrinogen, collagen type I and type IV, plasminogen and vitronectin bind to Helicobacter pylori . Radiolabelled vitronectin and plasminogen bound to the haemagglutinating H. pylori strain 17874 at a high level (53% and 32%, respectively), type IV collagen showed an intermediate level of binding (16%), while binding by 125 I‐labelled fibrinogen, fibronectin and collagen type I remained at a low level (5–7%). Both 125 I‐vitronectin and plasminogen showed a dose‐dependent binding to cells of H. pylori 17874. Plasminogen binding by this strain was specific since the binding was inhibited by nonlabelled plasminogen, but not by highly glycosylated glycoproteins such as fetuin and orosomucoid or by a variety of monosaccharides. We have previously shown that 125 I‐vitronectin shows a specific and saturable binding to H. pylori 17874, and that sialic acid‐rich glycoproteins such as fetuin and orosomucoid drastically reduced binding. We now report that a simultaneous incubation of 125 I‐vitronectin and 125 I‐plasminogen with cells of H. pylori 17874 showed a total binding approximately similar to the level of binding when either 125 I‐plasminogen, or 125 I‐vitronectin only were incubated with the bacterial cells. Nonlabelled vitronectin inhibited the binding of 125 I‐plasminogen by H. pylori , but nonlabelled plasminogen had no effect on the binding of 125 I‐vitronectin. Our findings suggest that there are different but probably closely localized binding sites for vitronectin and plasminogen on H. pylori 17874.