Properties of light and heavy vesicles simultaneously prepared from hog gastric mucosae

We obtained two kinds of vesicle preparations which were of different density from the same gastric mucosae of hogs stimulated with food before slaughter. Both kinds contained H⁺,K⁺-ATPase. The light vesicle preparation differed from the heavy vesicle preparation as follows: the KCl permeability across the membrane of heavy vesicles was larger than that of light vesicles, the actin (46-kDa peptide on SDS-polyacrylamide gel) content of heavy vesicles was much higher than that of light vesicles, and the H⁺,K⁺-ATPase activity of heavy vesicles was less sensitive to a monoclonal antibody raised against light vesicles (HK2032) than that of light vesicles. Furthermore, there was a drastic difference in reactivity to SCH 28080, which is an H⁺,K⁺-ATPase-specific inhibitor and reacts competitively with the K⁺-high affinity site. SCH 28080 is more potent in light vesicles than in heavy vesicles. These results suggest that the conformation of H⁺,K⁺-ATPase changed during the translocation from tubulovesicles to the apical plasma membrane. On the other hand, H⁺,K⁺-ATPase activities in both vesicles had similar pH and [K⁺] dependences.