Figure 5.

Stereoview of the P loop in FPGS (blue bonds) overlaid with the P loop from p21-ras (red bonds). The location of the pyrophosphate and the Mg²⁺ are given in black, superimposed on F_o–F_c omit density for the PPi and the Mg²⁺. The proposed location of the γ-phosphate is the lobe of F_o–F_c density between the PPi and the sidechain of Lys50. The conserved lysine residue in the P loop is indicated for FPGS (Lys50, magenta) and p21-ras (Lys16, orange), along with a conserved acidic residue adjacent to the active site, which is Glu143 in FPGS and is Asp57 in p21-ras. The first two residues of the Ω loop (Ser73 and Pro74) are indicated in cyan.