Cell adhesion is responsible for the formation of tissues and organs. Cadherins are proteins that confer specificity to cells such that they adhere only to specific cell types. They are membrane-bound calcium-binding proteins with independently folded extracellular domains that participate in the cell-cell interactions. Calcium binds at the interface between the extracellular domains and changes their relative disposition. Calcium is required for cell adhesion. Studies of cadherins fall into two main categories, cellular level studies and high-resolution structural studies. Results from these approaches have not yielded a paradigm for the structural basis of the intermolecular interactions. At this point there is little understanding of the energetics of the molecular interactions involving cadherins. This project includes the study of the stability and calcium-binding properties of the extracellular domains of epithelial cadherin. In addition, the project will address how the calcium-binding properties depend on dimerization. These studies will elucidate the energetic origins of the calcium-linked interactions of cadherin that are critical for cell adhesion. The specific aims of this research are: characterization of the stability of the extracellular domains of epithelial-cadherin (ECAD12), determination of affinity and cooperative interactions for calcium binding to the sites between ECAD12, and establishing conditions under which cis-dimerization occurs for ECAD12. This project will have a broad positive impact on undergraduate and graduate education in physical biochemistry.
