Fig. 9. VSV-G exiting the ER transiently associates with Sec31B-F. COS-7 cells were transiently transfected with VSV-G (construct 472, green) and eYFP-Sec31B-F (construct 787, yellow), colored red. After accumulating VSV-G in the ER for 3 hours at 40°C, cells were shifted to a permissive temperature (32°C) and images collected every 12 seconds over a period of 10 minutes. A selection of images at the times indicated is shown. The VSV-G can be seen filling the Golgi network. Also visible are many small transport vesicles exiting the ER and moving towards the Golgi network. The eYFP-Sec31B-F oscillates in the vicinity of ERESs but does not move towards the Golgi network. The insert, magnified 4x, demonstrates VSV-G and eYFP-Sec31B-F temporarily merged at the ERES; after 24 seconds the VSV-G vesicle moves anterograde towards the Golgi network, while eYFP-Sec31B-F stays behind. Arrows indicate the locus of a Sec31B-F vesicle (red) and a VSV-G-loaded vesicle (green). Bar, 10 µm.