The first part of this proposal is aimed at testing if Ail, a small outer membrane protein and a potential adhesion from human pathogen Yersinia enterocolitica, interacts directly with the mammalian cells to promote bacterial attachment and invasion. Under the presupposition that such direct interactions are real, as suggested by previous evidence, the second part of the proposal is designed to identify the receptor(s) for Ail. The long term goal of this project is to understand the signal transduction events triggered by the interactions between Ail and its receptor(s) that result in the internalization of the bacteria.