Fig. 5. Colocalization of VSVG-YFP and Sec31-CFP accumulation in ER exit site (ERES) membranes. (A) COS7 cells coexpressing VSVG-YFP (green) and Sec31-CFP (red) were treated as described in previous figures. Cells were transferred to the permissive temperature (34°C) and images were acquired at 2-minute intervals (see also supplementary material Movie 4). Scale bar: 10 µm. (B) Time-dependent increase in relative PFIVar of VSVG-YFP (green circles) and Sec31-CFP (red circles), calculated as described in the Materials and Methods, for the cell in A. Data were fitted to an exponential equation (y = ae^kx) (green and red lines for VSVG-YFP and Sec31-CFP, respectively). R² values were 0.98 and 0.97, and k values were 6.4 and 1.65% per minute, for VSVG and Sec31, respectively.