Golgi elements remain stable in shape, size, and position during a high flux of cargo exit A. Schematic of fluorescent transmembrane proteins used in this study, showing relative orientation, approximate location of protein domains, and placement of the fluorescent protein tag (cylinder). B. Golgi dynamics during a high flux of cargo exit. VSVG3-YFP was accumulated overnight in the ER of transiently transfected PtK2 cells and released synchronously into the secretory pathway by shifting to 32°C. Imaging was initiated after 27 minutes at 32°C, during the peak period of TC exit from the Golgi. The Golgi in PtK2 cells comprises scattered, separate elements near the MTOC. Comparison of single frames from the beginning of the movie (top panels) with projections over a 3 minute period (bottom panels) shows Golgi elements containing T2-CFP remain stable as VSVG3-YFP cargo exits the Golgi in TCs, which track outwards to the cell periphery. This figure corresponds the movies in Additional Fileset 1. Bar: 10 μm.