Fig. 1.

The allosteric switch in Ras. Ribbon diagram of Ras-GppNHp showing the shift in helix 3 and loop 7 due to the binding of calcium acetate in the allosteric site. Ras bound to calcium acetate is shown in green with a semitransparent surface. Note the presence of switch II in the model. Ras in the absence of calcium acetate is in yellow (PBD ID code 2RGE). The GppNHp and acetate (with van der Waals dot surface) are shown in stick. (Upper Left) Details of the calcium acetate binding site with a 2Fo-Fc electron density map contoured at the 1σ level. Dashed lines indicate H bonds and calcium ion coordination. All figures were generated in PyMol.