NMR studies of pig gastric microsomal H⁺,K⁺-ATPase and phospholipid dynamics. Effects of ethanol perturbation

The effects of ethanol on the gastric H⁺,K⁺-ATPase activity and the degree of mobility of various microsomal phospholipids were assessed using ³¹P and ¹H NMR. This illuminated the role of lipid-protein association in the function of pig gastric microsomes. Treatment of gastric microsomes with 15% ethanol for 1 min at 37°C inactivated the H⁺,K⁺-ATPase activity, which could largely be reconstituted by supplementation with phosphatidylcholine isolated from the gastric microsomes. Under similar conditions, the ¹H NMR profile of the microsomal ⁺N(CH₃)₃ choline moiety showed dramatic enhancement of peak intensity as well as a break point at 25°C which was restored to the untreated control value after reconstitution. This break, together with the dramatic enhancement in the overall lipid profile, compared to the control and reconstituted microsomes, suggested a greater degree of freedom of movement of the microsomal lipids following ethanol perturbation. The data demonstrate the unique ability that a combined approach using ³¹P and ¹H NMR holds as a noninvasive probe to study the structure-function relationship of biomembranes.