The conformational basis of energy transformations in membrane systems: IV. Energized states and pinocytosis in erythrocyte ghosts

Abstract

An energized change in shape which corresponds to pinocytosis has been observed by electron microscopy in erythrocyte ghosts obtained from cow, pig, and rabbit blood. This pinocytosis requires ATP and is not induced by the imposition of an external osmotic pressure; ITP will not replace ATP as an energizing agent. Ouabain, which inhibits energized sodium and potassium movements, does not prevent pinocytosis. Since the hydrolysis of ATP is required to energize the movement of ions across the red cell membrane, it is hypothesized that the pinocytosis observed is a result of a conformational change induced in membrane subunits when they are energized by ATP. The conformationally energized state could be a required step in the movement of ions across the membrane. It could give rise to the gross shape changes of pinocytosis only in a membrane which is freed from normal constraints, as is the case for the erythrocyte ghost.