Yeagle P L, Young J, Rice D
Department of Biochemistry, State University of New York, Buffalo 14214.
Biochemistry. 1988 Aug 23;27(17):6449-52. doi: 10.1021/bi00417a037.
The (Na+,K+)-ATPase ATP hydrolyzing activity from rabbit kidney medulla basolateral membrane vesicles was studied as a function of the cholesterol content of the basolateral membranes. The cholesterol content of the membranes was modified by incubation with phospholipid vesicles. When the cholesterol content was increased above that found in the native membrane, the (Na+,K+)-ATPase ATP hydrolyzing activity was inhibited. When the cholesterol content was decreased from that found in the native membranes, the (Na+,K+)-ATPase ATP hydrolyzing activity was inhibited. Analogous effects were found with the K+-activated phosphatase activity of the same membrane vesicles. Therefore, at low cholesterol contents, cholesterol was stimulatory, and at high cholesterol contents, cholesterol was inhibitory. The structural specificity of this effect was tested by introducing lanosterol and ergosterol as 50% of the membrane sterol. Ergosterol was the least effective at supporting (Na+,K+)-ATPase ATP hydrolyzing activity, while lanosterol was more effective, but still not as effective as cholesterol.
研究了兔肾髓质基底外侧膜囊泡中（Na +，K +）-ATP酶的ATP水解活性与基底外侧膜胆固醇含量的关系。通过与磷脂囊泡孵育来改变膜的胆固醇含量。当胆固醇含量增加到高于天然膜中的含量时，（Na +，K +）-ATP酶的ATP水解活性受到抑制。当胆固醇含量从天然膜中的含量降低时，（Na +，K +）-ATP酶的ATP水解活性也受到抑制。在相同膜囊泡的K +激活磷酸酶活性中也发现了类似的效应。因此，在低胆固醇含量时，胆固醇具有刺激作用，而在高胆固醇含量时，胆固醇具有抑制作用。通过引入羊毛甾醇和麦角甾醇作为膜甾醇的50%来测试这种效应的结构特异性。麦角甾醇在支持（Na +，K +）-ATP酶的ATP水解活性方面效果最差，而羊毛甾醇效果更好，但仍不如胆固醇有效。
