Bacterial adhesins play a crucial role in pathogen-host interactions, initiating infections by adhesion to the extracellular matrix and to cell surface proteins prior to invasion. A family of non-fimbrial adhesins, the trimeric autotransporter adhesins (TAAs), has recently been described in gram-negative pathogens. The common biological role of all these TAAs is to mediate the interaction of pathogenic bacteria with their hosts. There is an increasing body of evidence that TAAs represent highly important bacterial pathogenicity factors. Typically TAAs are long, fibrous proteins. They are constructed of a set of repetitive modules or domains that are combined in a fashion of building blocks to meet the individual needs of the pathogen. There is detailed structural and functional information for only a few TAA domains at present. The head domain structure of YadA from Yersinia enterocolitica was solved in Goldman group and motifs were identified that contribute to collagen binding. YadA is an autotransporter, with a globular head, a coiled coil stalk and a C-terminal membrane anchor/translocator. The aim of the proposed project is to: 1. Understand how the β-barrel translolates the passenger domain. 2. Understand the folding mechanism of the β-barrel. 3. Determine the structure of the YadA transmembrane domain in complex with with a collagen peptides.