Figure 4. Surface rendering depicting cysteine solvent-accessible residues (yellow) in Rho family GTPases (see Table 1). (A) Left panel, Rac1 (PDB 3TH5) flipped by 180° around the y-axis. Right panel, close-up of the nucleotide-binding site with the redox-sensitive thiol (Cys¹⁸) shown. Other local thiols are labeled (note that Cys⁸¹ is not solvent-accessible). Distances are presented in Å from the reactive thiol to the nucleotide. (B) RhoA surface rendering (PDB 1A2B). Images are as in (A). The close-up of the nucleotide-binding pocket (right panel) shows the redox-sensitive thiol (Cys²⁰) as well as other local thiols. (C) Cdc42 surface rendering (PDB 2QRZ). Images are as in (A). The close-up of the nucleotide-binding pocket (right panel) highlights Cys.¹⁸