Left bars – apparent fraction of ERGIC marker colocalizing with the three proteins at 37°C. Right bars- apparent fraction of ERGIC marker colocalizing with the three proteins at 15°C. The reduction in colocalization of ERGIC-53 with the other markers at 15°C reflects the temperature-induced block in cycling of ERGIC-53 between the ERGIC and the ER (27). Note that this block affects colocalization of ERGIC-53 and Bap31, much less than it affects the colocalization of ERGIC-53 with calnexin, an ER-resident protein. The result for ERGIC-53 and Bap29 is similar to that for ERGIC-53 and calnexin, which implies that Bap29, like calnexin, is restricted to the ER. The data are averages for 20 (15°C) and 35 (37°C) cells.