FIGURE 6:
The CTCD alters the interaction between Sec23 and Sec31. (A) The GTPase activity of Sar1 was examined with MBP-Sec161639-2195 (150 nM) as in Figure 3B. Where indicated, Sec13/31 was added in the starting mixture. (B) Sar1 GTPase activity was monitored with the indicated concentrations of MBP-Sec161639-2195 in the presence of Sec13/31 as in A. (C) Sar1 GTPase activity was monitored with indicated MBP-Sec16 in the presence of Sec13/31 as in A. (D) Liposome-binding assay of COPII proteins with MBP-Sec161639-2195. Sar1 (800 nM), Sec23/24 (100 nM), Sec13/31 (150 nM), and MBP-Sec161639-2195 (300 nM) were incubated with GDP or GMP-PNP (100 μM) and synthetic liposomes (100 μg/ml) subjected to flotation on a sucrose density gradient. Float fractions were subjected to SDS–PAGE and stained with Sypro Orange.