The glycine brace within crystal structures of representative Rab-related GTPases. Color scheme: backbone of the P-loop region, dark red; backbone of the glycine brace region, dark yellow; backbone of the guanine-binding loop region, green; side chains of residues characteristic of P-loop GTPases, magenta; side chains of residues characteristic of the Rab-related GTPases, yellow. (A) The Rab-family GTPase Rab11A bound to a GTP analog (GTPγS) (pdb_id: 1oiw). (B) The Rho/Rac family GTPase Rac1 bound to a GTP analog (pdb_id: 1i4t) . (C) Ran GTPase bound to GDP (pdb_id: 1byu) . (D) Ran GTPase bound to its exchange factor RCC1 (pdb_id: 1i2m) .