FIG. 7.

RanGAP-catalyzed hydrolysis of Ran-GTP. (A) Ran47-GTP (1.5 μM) was mixed at a 1:1 ratio (vol/vol) with RanGAP in the stopped-flow apparatus (only three curves are shown). The fluorescence transients were fitted as single exponentials. (B) Plot of rate constants (•) versus [RanGAP]. Assuming a simple saturation model (16) and given that k_off ≫ k_cat, the observed rate constants can be fitted to a quadratic equation (K_d = 1.0 μM; k_cat = 7.9 s⁻¹). Measurements were performed and analyzed as described in Materials and Methods.