Abstract
In the presence of both ATP and Mg++, the density of the negative charge on the external surface of hog gastric vesicles had a higher (absolute) value in comparison to values in the presence of ATP only or the absence of both ATP and Mg++ as seen from the electrophoretic mobilities measured with a conventional cytopherometer. Gastric vesicle-coated particles of n-alkanes or n-alky1 halides were used for the study, in which their surfaces were examined under differential interference-contrast microscopy. This showed that the surfaces were coated by the vesicles. On the addition of Mg-ATP, an increase in the density of the surface charge took place irrespective of the oil used. With n-alkyl bromide (<0.1 % v/v), reorganization of the vesicular structure was indicated from the measurements of proton uptake by the vesicles. This uptake was followed by an increase in the proton leakiness of the membrane. This is evidence that the increased density of the negative charge of the vesicle surface is not due to the proton gradient but with most to phosphorylation of the K+-ATPase in the gastric vesicles. The temperature dependence of the viscosity-corrected electrophoretic mobility showed that there was some transition about 23°C in the presence of Mg-ATP, but not in the absence of Mg-ATP.
