Figure 3.

Bet3-associated GEF activity for Ypt32, but not Sec4. GST-Bet3 (▴) or GST (●) were purified from yeast cells and tested for Ypt32 and Sec4 GEF activity using GDP-release and GTP-uptake filtration assays and recombinant Ypt32 or Sec4 protein (as described in Figure 1 legend). (a) Time course of GDP release from Ypt32p. (b) Time course of GTP uptake by Ypt32p, in the presence (solid lines) or absence (dashed lines) of Ypt32p. (c) Time course of GDP release from Sec4p. GST-Sec2 (squares) was used as a positive control for a Sec4-GEF. The data is expressed as percent GDP bound to Sec4p during the reaction. Results shown in this figure are the average of duplicate measurements and are representative of 2–4 experiments. Error bars represent range divided by 2.