Animal plasma membrane energization by proton motive V-ATPases

Proton-translocating, vacuolar-type ATPases, well known energizers of eukar yotic, vacuolar membranes, now emerge as energizers of many plasma membrane s. Just as Na+ gradients, imposed by Na+/K+ ATPases, energize basolateral p lasma membranes of epithelia, so voltage gradients, imposed by H+ V-ATPases , energize apical plasma membranes. The energized membranes acidify or alka linize compartments, absorb or secrete ions and fluids, and underwrite cell ular homeostasis. V-ATPases acidify extracellular spaces of single cells su ch as phagocytes and osteoclasts and of polarized epithelia, such as verteb rate kidney and epididymis. They alkalinize extracellular spaces of lepidop teran midgut. V-ATPases energize fluid secretion by insect Malpighian tubul es and fluid absorption by insect oocytes. They hyperpolarize external plas ma membranes for Na+ uptake by amphibian skin and fish gills. Indeed, it is likely that ion uptake by osmotically active membranes of all fresh water organisms is energized by V-ATPases. Awareness of plasma membrane energizat ion by V-ATPases provides new perspectives for basic science and presents n ew opportunities for medicine and agriculture. BioEssays 21.637-648, 1999. (C) 1999 John Wiley & Sons, Inc.