YadA, the multifaceted Yersinia adhesin

The adhesion protein YadA is encoded by the yadA gene located in the 70-kb virulence plasmid of Yersinia (pYV) that is common to the pathogenic Yersin ia species (Y. pestis, Y. pseudotuberculosis and Y. enterocolitica). YadA i s a virulence factor of Y enterocolitica, however, YadA seems to be dispens able for the virulence of Y. pseudotuberculosis, and in wild-type. Y. pesti s the yadA gene has a frameshift mutation silencing the gene. Expression of the Y pseudotuberculosis YadA in Y pestis reduces its virulence. YadA is a homotrimer of ca. 45-kDa subunits that are anchored to the outer membrane via their C-termini, while their N-termini form a globular head on top of a stalk; the 'lollipop'-shaped YadA structure covers the entire bacterial su rface giving it hydrophobic properties. The yadA gene expression is induced at 37 degreesC by the temperature-dependent transcriptional activator LcrR . YadA is a multifaceted protein as revealed by its different biological pr operties. YadA(+) bacteria bind to collagens, laminin, fibronectin, intesti nal submucosa, mucus, and to hydrophobic surfaces like polystyrene. YadA(+) bacteria autoagglutinate in stationary culture and also specifically agglu tinate guinea pig red blood cells. YadA is also a potent serum resistance f actor as it inhibits the classical pathway of complement. As invasin, it me diates low rate invasion to tissue culture cells. In a rat model of reactiv e arthritis YadA and specifically YadA-mediated collagen binding is necessa ry for Y. enterocolitica to induce the disease. Despite of this wealth of i nformation or perhaps because of it, the in vivo role of YadA during infect ion remains still largely unresolved.