Manipulation of the phosphatidylethanolamine pool in the human red cell membrane affects its Mg²⁺-ATPase activity

Summary

Decreasing the size of the outer leaflet pool of phosphatidyletha-nolamine (PE) in the erythrocyte membrane by treatment of intact cells with either phospholipase A₂ or trinitrobenzenesul-phonic acid (TNBS), causes a corresponding decrease in Mg²⁺ -ATPase activity as determined in their respective ghosts. Also, incubation of ghosts with Ro09–0198, a cyclic peptide from Streptoverticillium which is known to interact specifically with PE, causes a decrease in Mg²⁺-ATPase activity which is dependent on the amount of peptide added. These three different approaches, all causing a decrease in endogenous PE, thus result in a concomitant decrease in Mg²⁺-ATPase activity which reaches a plateau level at approximately 25% residual activity. Hence, it is inferred that the complementary fraction (75%) of the total Mg²⁺-ATPase in the red cell membrane is closely related to the functioning of its aminophospholipid specific translocase as it mediates a (continuous) transport of PE molecules from outer to inner membrane leaflet. This view is supported by the observation that an increase in the total amount of PE in the membrane by decarboxylation of an appreciable fraction of its PS, results in a considerable increase in Mg²⁺-ATPase activity.

Key Words:

• Erythrocytes
• membrane phospholipid asymmetry
• aminophospholipid translocase
• phosphatidylethanolamine
• Mg²⁺-ATPase