ABSTRACT
Proton-motive vacuolar-class ATPases (V-ATPases) are commonly associated with membrane-bound organelles other than mitochondria and chloroplasts. They are found in the vacuoles of Neurospora crassa and yeasts, in tonoplasts of plants and in endomembranes such as lysosomes, endosomes, clathrin-coated vesicles and secretory granules (Sze, 1985; Rudnick, 1986; Mellman et al. 1986; Rodman et al. 1991). However, they have also been found in plasma membranes of kidney tubules (Brown et al. 1987; Wang and Gluck, 1990). Recently, the pump responsible for the large lumen-directed net flux of potassium across larval Manduca sexta midgut has been shown to consist of a plasma membrane protonmotive V-ATPase functioning in conjunction with an nH+/K+ antiporter (Wieczorek et al. 1991).
