A comparison of the influence of sterols on the specific activity of the H+-ATPases in isolated plasma membrane vesicles from oat, rye and rice shoots

Plasma membrane vesicles were extracted from the shoots of 10-day-old oat, rye and rice plants and incubated with either cholesterol, stigmasterol or a mixture of sitosterol ⁺ campesterol (60:40). After ascertaining that the sterol composition of the vesicles had been altered by this treatment, the specific hydrolytic activity of the membrane-bound H⁺-ATPase (EC 3. 6. 1. 35) was measured. The results indicated that, although all sterols were taken up, cholesterol was best integrated into the plasma membrane of the species tested. After treatment, ATPase activity was altered in oat and rice, but not in rye. The results are discussed in the context of sterol/lipid and sterol/protein interactions in the plasma membrane.