Focal Adhesion Kinase (FAK) is a central scaffolding and catalytic component of integrin and growtl factor signaling pathways. Proper FAK function is required for remodeling of focal contacts and for cell motility in diverse normal and pathological contexts including vascular morphogenesis, platelet spreading, cytotrophoblast migration, and tumor metastasis. Our long-term goal is to structurally define the molecular interactions of FAK, and to elucidate the mechanisms by which it is activated in response to integrin and growth factor engagement. These studies will provide a structural foundation for design of novel FAK- specific inhibitors, which may be useful as anti-thrombotic or anti-metastatic agents. As described in our preliminary results, we have determined the crystal structure of the N-terminal "PERM" domain of FAK, a domain found in many cytoskeletal and signaling proteins that is thought to mediate protein-protein and protein-lipid interactions. The structure suggests that binding of protein ligands to the FAK PERM domain may be regulated by docking of the SH3 and SH2 domains of Src at an adjacent site. In Aim 1, we will test this hypothesis and work to structurally define the interaction of the FAK PERM domain with the cytoplasmic region of (3-integrins and with the EGF receptor. In Aim 2, we will expand upon our discovery that the FAK PERM domain binds phosphoinositides with further studies of its phospho-specificity and with crystallographic analysis of FERM/phosphoinositide complexes. In Aim 3, we will determine the structural basis for the recently reported FERM-mediated autoinhibiton of FAK. Toward this Aim, we have expressed, purified, and obtained preliminary crystals of a multidomain FAK fragment that includes both the PERM and tyrosine kinase domains. For each Aim, collaborations with the Springer and Schaller labs will facilitate structure/function studies in a cellular context that will be crucial for interpreting our structural results and their implications for integrin signaling.