Fig. 2. Crystal structure of Par6B(126–253) bound to Cdc42(Q61L)·GMPPNP at 2.1 Å resolution. Ribbon diagram with Cdc42 colored blue and Par6 yellow (left and center images). A structure of the WASP–Cdc42 complex (Abdul-Manan et al., 1999) is also shown on the right, for comparison. The Switch I and II regions of Cdc42 are colored red, the semi-CRIB motif of Par6 and the CRIB motif of WASP are colored black, and the GMP-PNP/Mg²⁺(H₂O)₂ moiety is presented in ball-and-stick representation. A short region of the PDZ domain of Par6 (residues 204–208) that makes contact with Cdc42 is highlighted in magenta. The center image is of the complex rotated by 90° about the vertical axis. The black arrow indicates the location of the PDZ ligand-binding pocket.