Fig. 1. Organization of the domains of focal adhesion kinase. The N-terminal domain shares similarity with members of the FERM homology domain family of proteins and directs interactions with integrins and growth factor receptors. The central domain is the catalytic domain. The C-terminal domain contains sites for multiple protein-protein interactions. Site I (SI) is an interaction site for the SH3 domain of Cas; site II (SII) is the site of interaction with the SH3 domains of GRAF and ASAP. Y397 is the major site of autophosphorylation and a site of interaction with the SH2 domain of Src. FAT denotes the region required for focal adhesion targeting. The inset illustrates the four helical bundle that makes up the FAT domain. Paxillin interacts within sequences with the FAT domain; these sequences are denoted in yellow in the FAT structure. Additional sites of tyrosine and serine phosphorylation are indicated.