A SECRETED SALMONELLA PROTEIN WITH HOMOLOGY TO AN AVIRULENCE DETERMINANT OF PLANT-PATHOGENIC BACTERIA

Bacterial pathogens have evolved sophisticated mechanisms to interact with their hosts. A specialized type III protein secretion system capa ble of translocating bacterial proteins into host cells has emerged as a central factor in the interaction between a variety of mammalian an d plant pathogenic bacteria with their hosts. Here we describe AvrA, a navel target of the centisome 63 type III protein secretion system of Salmonella enterica. AvrA shares sequence similarity with YopJ of the animal pathogen Yersinia pseudotuberculosis and AvrRxv of the plant p athogen Xanthomonas campestris pv. vesicatoria. These proteins are the first examples of putative targets of type III secretion systems in a nimal and plant pathogenic bacteria that share sequence similarity. Th ey may therefore constitute a novel family of effector proteins with r elated functions in the cross-talk of these pathogens with their hosts .