BINDING OF VITRONECTIN AND PLASMINOGEN TO HELICOBACTER-PYLORI

We have studied how some extracellular matrix proteins, fibronectin, f ibrinogen, collagen type I and type IV, plasminogen and vitronectin bi nd to Helicobacter pylori. Radiolabelled vitronectin and plasminogen b ound to the haemagglutinating H. pylori strain 17874 at a high level ( 53% and 32%, respectively), type IV collagen showed an intermediate le vel of binding (16%), while binding by I-125-labelled fibrinogen, fibr onectin and collagen type I remained at a low level (5-7%). Both I-125 -vitronectin and plasminogen showed a dose-dependent binding to cells of H. pylori 17874. Plasminogen binding by this strain was specific si nce the binding was inhibited by nonlabelled plasminogen, but not by h ighly glycosylated glycoproteins such as fetuin and orosomucoid or by a variety of monosaccharides. We have previously shown that I-125-vitr onectin shows a specific and saturable binding to H. pylori 17874, and that sialic acid-rich glycoproteins such as fetuin and orosomucoid dr astically reduced binding. We now report that a simultaneous incubatio n of I-125-vitronectin and I-125-plasminogen with cells of H. pylori 1 7874 showed a total binding approximately similar to the level of bind ing when either I-125-plasminogen, or I-125-vitronectin only were incu bated with the bacterial cells. Nonlabelled vitronectin inhibited the binding of I-125-plasminogen by H. pylori, but nonlabelled plasminogen had no effect on the binding of I-125-vitronectin. Our findings sugge st that there are different but probably closely localized binding sit es for vitronectin and plasminogen on H. pylori 17874.