Is there a plasma membrane-located anion-sensitive ATPase?

A study of the intracellular localization of HCO-3-stimulated, SCN--inhibited magnesium-dependent ATPase was performed in gill tissue of the rainbow trout (Salmo irideus), rabbit kidney and rabbit gastric mucosa. Tissue homogenates were subjected to centrifugal fractionation, and the microsomal (60 min 100 000 X g) and light mitochondrial (20 min 20 000 X g) fractions were further fractionated by density gradient centrifugation. Subfractions were characterized by marker enzyme assays and electron microscopic observation. In trout gill indications for an exclusively mitochondrial localization were found. In kidney no definite conclusions could be drawn. In rabbit gastric mucosa initially an apparently non-mitochondrial HCO-3-stimulated ATPase, in addition to a mitochondrial one, was found and its characteristics were studied. Further studies showed that this ATPase also appears to be of mitochondrial origin and probably represents mitochondrial inner membranes. Possible explanations for earlier conflicting reports concerning the localization of this enzyme in gastric mucosa and other tissues are discussed.