Two-dimensional separations of G-proteins. Proteins were extracted with 750 mm KCl from untreated or ethylene-treated (1 μL L−1) epicotyls and separated by two-dimensional gel electrophoresis. A, Designation of spots; B, quantification of GTP binding during time course: 2 (●), 6 (♦), 8 (▪), 9 (○), 12 (▵), 14 (□).