Fig. 3. The v-SNARE, Bos1p, is less efficiently sorted into COPII vesicles in a vma21 deletion strain than in the wild type. (A) Microsomes from wild-type (BY4742), erv46 (SOY01409) or vma21 (SOY01629) strains were incubated without (–) or with (+) purified COPII subunits in presence of GTP and an ATP regeneration system. Membranes from 10% of the total reaction (T) and vesicle fractions were collected by centrifugation and detected by western blotting with antibodies against various vesicle proteins as well as the ER resident, Sec12p, as a negative control. A line marks the Erv29p band among bands cross-reacting with the polyclonal antiserum. (B,C) Densitometric analysis of three independent experiments performed as in A. Mean packaging efficiencies as a percentage of input were plotted, and error bars represent the standard deviation.