Intimin from Shiga toxin-producing Escherichia coli and its isolated C-terminal domain exhibit different binding properties for Tir and a eukaryotic surface receptor

The outer membrane protein intimin plays a crucial role in the attaching an d effacing process employed by different enteropathogens to colonize the ep ithelial surface of their hosts. In this study we have characterized the C- terminal binding domain of intimin from the Shiga toxin-producing Escherich ia coli strain 413/89-1, that belongs to the beta -subtype of intimins. We found that a fusion of this domain to the maltose-binding protein binds eff iciently to both the translocated intimin receptor (Tir) and the surface of uninfected eukaryotic host cells. In contrast, no such binding was observe d with the full-length protein localized on the bacterial surface. As the C -terminal domain of intimin and the full-length protein differ in their bin ding activity, we suggest that the intimin binding domain might be controll ed by the N-terminal portion of the molecule to prevent unproductive intera ctions with molecules in the lumen of the gut.