The structural basis of Rho effector recognition revealed by the crystal structure of human RhoA complexed with the effector domain of PKN/PRK1

The small G protein Rho has emerged as a key regulator of cellular events i nvolving cytoskeletal reorganization. Here we report the 2.2 Angstrom cryst al structure of RhoA bound to an effector domain of protein kinase PKN/PRK1 . The structure reveals the antiparallel coiled-coil finger (ACC finger) fo ld of the effector domain that binds to the Rho specificity-determining reg ions containing switch I, beta strands B2 and B3, and the C-terminal alpha helix A5, predominantly by specific hydrogen bonds. The ACC finger fold is distinct from those for other small G proteins and provides evidence for th e diverse ways of effector recognition. Sequence analysis based on the stru cture suggests that the ACC finger fold is widespread in Rho effector prote ins.