Fig. 8. GEF activity of Kalirin is increased by mutation of Thr1590 to Asp. GEF activity was assessed in vitro using GDP-Mant-loaded Rac1 (2 µM). (A) Change in fluorescence over time. Buffer or the proteins indicated (final concentration 20 µM) were added at t=3 minutes. (B) Data from the first 20 minutes converted to a semi-logarithmic plot enabled initial rate calculation. (C) Data from three assays for GEF activities of GST-KGEF1-K7end, KGEF1-K7end T/A and KGEF1-K7end T/D were averaged. Significant differences are indicated; ^*P<0.05.