SUBSTITUTION OF 2 HISTIDINE-RESIDUES IN YADA PROTEIN OF YERSINIA-ENTEROCOLITICA ABROGATES COLLAGEN-BINDING, CELL ADHERENCE AND MOUSE VIRULENCE

The plasmid-encoded surface protein YadA of Yersinia enterocolitica me diates binding to diverse extracellular matrix (ECM) proteins, adheren ce to epithelial cell lines, resistance to complement lysis, autoagglu tination, and is required for mouse virulence. Using site-directed mut agenesis we attempted to analyse the relationship between structural d omains and functions of YadA. In a first approach we could abrogate co llagen binding by chemical modification of histidyl residues of YadA p rotein. This result prompted us to substitute histidyl residues (His) of conserved regions of YadA protein of Y. enterocolitica O8 by tyrosi ne residues using site-directed mutagenesis. Substitution of His-156 a nd His-159 (YadA-2 mutant) resulted in abrogation of binding to ECM pr oteins, of cell adherence, and in reduction of mouse virulence, wherea s autoagglutination, serum complement resistance and oligomer formatio n remained unaffected. A striking result was obtained from the orogast ric mouse-infection model: the YadA-2 mutant retained the ability to c olonize the small intestine and to invade and multiply within the Peye r's patches but was impaired in colonizing mesenteric lymph nodes and spleen in comparison to the wild-type strain.