Crystal structures of the outer membrane domain of intimin and invasin from enterohemorrhagic E. coli and enteropathogenic Y. pseudotuberculosis.

Intimins and invasins are virulence factors produced by pathogenic Gram-negative bacteria. They contain C-terminal extracellular passenger domains that are involved in adhesion to host cells and N-terminal β domains that are embedded in the outer membrane. Here, we identify the domain boundaries of an E. coli intimin β domain and use this information to solve its structure and the β domain structure of a Y. pseudotuberculosis invasin. Both β domain structures crystallized as monomers and reveal that the previous range of residues assigned to the β domain also includes a protease-resistant domain that is part of the passenger. Additionally, we identify 146 nonredundant representative members of the intimin/invasin family based on the boundaries of the highly conserved intimin and invasin β domains. We then use this set of sequences along with our structural data to find and map the evolutionarily constrained residues within the β domain.