Fig. 1. Rab5(Q79L) induces the formation of giant endosomes in RAW264.7 macrophages. The effect of the rab5(Q79L) mutation on the morphology of endosomes (e) in RAW264.7 macrophages was examined at the electron microscope. Internalization of HRP (10 mg/ml) for 30 minutes in control (A) or rab5(Q79L)-expressing cells (B) led to the accumulation of this tracer in small vesicles in control cells (A), while it was found in very large endosomes (e) in mutant cells (B). Bar, 0.5 µm.