Featured Species-Specific Loops Are Found in the Crystal Structure of Eno， a Cell Surface Adhesin From .

Enolase is an evolutionarily conserved enzyme involved in the processes of glycolysis and gluconeogenesis. belongs to ， whose species are wall-less and among the smallest self-replicating bacteria， and is an important colonizing respiratory pathogen in the pig industry worldwide. enolase ( Eno) expression is significantly increased after infection and was previously found to be a virulence factor candidate. Our studies show that Eno is a cell surface-localized protein that can adhere to swine tracheal epithelial cells (STECs). Adhesion to STECs can be specifically inhibited by an Eno antibody. Eno can recognize and interact with plasminogen with high affinity. Here， the first crystal structure of the mycoplasmal enolase from was determined. The structure showed unique features of Eno in the S3/H1， H6/S6， H7/H8， and H13 regions. All of these regions were longer than those of other enolases and were exposed on the Eno surface， making them accessible to host molecules. These results show that Eno has specific structural characteristics and acts as a multifunctional adhesin on the cell surface.