Figure 8.

Sey1p acts before Sec22p during homotypic ER fusion. Gluc1 and Gluc2 microsomes were incubated at 27°C in the presence of both ATP and GTP (A) or GTP alone (B). At the indicated times, a portion of the reaction received anti-Sey1p (squares) or anti-Sec22p (triangles) antibodies, or was placed on ice (circles). Luciferase activity was measured after 120 min. Fusion values were normalized to those obtained in reactions that received antibodies or were placed on ice at 120 min. Data represent the means ± SEM (error bars; n = 3). *, P < 0.05; **, P < 0.01; ***, P < 0.001, Tukey’s test compared with the ice groups (circles). (C) Similar sensitivity kinetics was observed with increasing amounts of anti-Sey1p antibodies. Gluc1 and Gluc2 microsomes were incubated at 27°C in the presence of GTP. At the indicated times, a portion of the reaction received increasing concentrations of anti-Sey1p antibodies (88 nM for squares, 176 nM for triangles, 352 nM for diamonds) or was placed on ice (circles). Luciferase activity was measured after 120 min. Data represent the means ± SEM (error bars; n = 3). *, P < 0.05; **, P < 0.01, Tukey’s test.