Overexpressed calnuc-GFP is concentrated in light membrane fractions containing plasma membranes and Golgi membranes. (A) Majority (90%) of the endogenous calnuc (NT) is in light fractions 10–12 containing Golgi and PM, with the remaining 10% found in heavy fractions (3–8). Calnuc-GFP is similarly concentrated in light fractions (75%), but some (25%) is also found in heavy fractions 3–8 containing ER and RSG, where it cosediments with synaptobrevin 2 (Vamp 2) and ACTH, a marker for RSG. No major change in the distribution of Vamp 2 and ACTH is observed following overexpression of calnuc-GFP. The ER marker calnexin and the Golgi marker α-mannosidase II (Man II) are found in heavy fractions (3–8) and light fractions (9–12), respectively. Overexpression of calnuc-GFP was not found to significantly change the distribution of ACTH and Vamp in the gradients. The percent of the total for a given protein in each quantified fraction was plotted in (B). The amount of each protein found in fractions 3–8 and 10–12 were pooled and plotted in the bar graph as the percent of total as shown in (C). Similar distribution change of indicated proteins was observed in 3 separate experiments depicted.