The Bin/Amphiphysin/Rvs (BAR) domain of GTPase Regulator Associated with Focal adhesion kinase
BAR domains are dimerization, lipid binding and curvature sensing modules found in many different proteins with diverse functions. GTPase Regulator Associated with Focal adhesion kinase (GRAF), also called Rho GTPase activating protein 26 (ARHGAP26), is a GAP with activity towards RhoA and Cdc42 and is only weakly active towards Rac1. It influences Rho-mediated cytoskeletal rearrangements and binds focal adhesion kinase (FAK), which is a critical component of integrin signaling. GRAF contains an N-terminal BAR domain, followed by a Pleckstrin homology (PH) domain, a Rho GAP domain, and a C-terminal SH3 domain. BAR domains form dimers that bind to membranes, induce membrane bending and curvature, and may also be involved in protein-protein interactions. The BAR domain of GRAF directly interacts with its Rho GAP domain and inhibits its activity. Autoinhibited GRAF is capable of binding membranes and tubulating liposomes, showing that the membrane-tubulation and GAP-inhibitory functions of the BAR domain can occur simultaneously.