Fig. 4. Kinetics of ER exit of Tac/UP chimeric proteins. (A) Schematic drawing of the Tac antigen, a type I transmembrane protein and of Tac/UP chimeric proteins. (B) HeLa cells expressing Tac/UP chimeric proteins were pulse-labeled with [35S]methionine for 15 minutes and then chased for 0 to 3 hours. The total cell lysates were harvested and subjected to immunoprecipitation using an anti-Tac antibody, followed by Endo H treatment. The Endo-H-treated samples were analyzed by SDS-PAGE and autoradiography. (C) The percentage of cells showing Endo-H resistance was calculated from densitometry values. The experiments were repeated three times to calculate s.e.m., which are indicated by the error bars. Statistical analysis was done using statistical computing software R 2.3.1.