N-CGB is required for secretory vesicle biogenesis. CGB fragments were expressed in NIH3T3 cells and stained for CGB (green) and vesicles (β-COP, red). A, CGB full-length; B, N-CGB; C, C-def-CGB; D, N-def-CGB; E, scrambled C-terminal CGB fragment (sc-CGB); F, when vesicles were quantified, N-CGB, CGB full-length, and C-def-CGB were shown to induce vesicle biogenesis, whereas N-def-CGB did not increase vesicle biogenesis over control (scrambled C-terminal CGB fragment). Data are mean ± S.E.; *, p ≤ 0.05; **, p ≤ 0.03; ***, p ≤ 0.01.