TRANSPORT CHARACTERISTICS OF FROG GASTRIC MEMBRANES

ATP-induced transport by fractions of frog gastric microsomes prepared either by density gradient centrifugation or by free flow electrophoresis were K+ dependent and hence considered due to a K+-activated ATPase. Significant activity of this enzyme was, however, only found in the anodic peak of the free flow electrophoretic separation, which in addition to separating transporting from non-transporting particles, also separated membranes containing a phosphorylatable peptide (Mr = 105 000) region as the major peptide on SDS-polyacrylamide gel electrophoresis from those containing a peptide (Mr = 44 000) on SDS-polyacrylamide gel electrophoresis. H+ uptake, measured either by acridine orange or 3,3′-diethyloxadicarbocyanine + tetrachlorosalicylanilide absorbance changes was dependent on K+ intravesicularly. Using 86Rb+, active extrusion of the cation followed ATP addition. SCN-, an inhibitor of acid secretion did not affect the latter, but blocked signals due to H+ uptake, in contrast to mammalian preparations. © 1979.