Fig. 3. Localization of the vacuolar H⁺-ATPase in lvsA cells. Wild-type (A,C) or lvsA mutant cells (B,D) were fixed and labeled by immunofluorescence with the indicated antibodies. The top panel in (A) represents labeling in a plane close to the substrate, whereas in other panels pictures correspond to a plane towards the middle of the cell body. The circles indicate the contractile vacuole (Rh50⁺, HATPase⁺, p80^-), the arrows the early endocytic compartment (Rh50^-, HATPase⁺, p80^low) and the arrowheads the late endocytic compartment (Rh50^-, HATPase^-, p80^high). Scale bar, 10 µm.