Coat-Dependent Vesicles, Their Content and Origin: Size Matters

The characteristics of cell small membrane spheres (vesicles) have not been fully explored to date. Here, we found that the distribution of diameters of these vesicles exhibits distinct peaks at 42, 50-52, 60, 70, 80, and 100 nm, which with the exception of the 50-nm vesicles can be inscribed into stable fullerenes, namely C₆₀, C₇₂, C₈₄, C₉₆, and C₁₃₄, respectively. Coated 50-52 and 100 nm vesicles were not found. The 60-, 70-, and 80-nm vesicles could be clathrin-coated or uncoated. These are accessible to WGA added externally. The COPI- or COPII-coated vesicles were not found. The concentration of resident proteins in the 50-52-nm vesicles is lower than in ER exit sites and Golgi membranes. These vesicles do not contain Sec22 but are enriched in GS27 and could bind Sec13. The vesicles isolated in the vesicular fraction share similar features. The formation of vesicles could stimulate membrane uncoating. Thus, the vesicle size is important.