This entry represents the HR1 (homology region 1) domain found in TOCA family proteins including TOCA1, CIP4, and FBP17. This domain forms an antiparallel coiled-coil structure that mediates binding to the small GTPase Cdc42. Unlike other HR1 domains ...
This entry represents the HR1 (homology region 1) domain found in TOCA family proteins including TOCA1, CIP4, and FBP17. This domain forms an antiparallel coiled-coil structure that mediates binding to the small GTPase Cdc42. Unlike other HR1 domains that bind to RhoA or Rac1 with high affinity, the TOCA family HR1 domains bind Cdc42 with relatively low (micromolar) affinity. The domain contains two alpha-helices connected by a loop region. The binding interface with Cdc42 includes both helices and the connecting loop. NMR studies suggest that the TOCA1 HR1 domain can be displaced from Cdc42 by the N-WASP GBD domain, suggesting an effector handover mechanism in which TOCA1 binding to Cdc42 positions N-WASP and Cdc42 for subsequent high-affinity interaction to initiate actin polymerization.
