肌浆网中的胆固醇与膜流动性的生理意义。
Cholesterol in sarcoplasmic reticulum and the physiological significance of membrane fluidity.
作者信息
Johannsson A, Keightley C A, Smith G A, Metcalfe J C
出版信息
Biochem J. 1981 May 15;196(2):505-11. doi: 10.1042/bj1960505.
Vesicles of sarcoplasmic reticulum from rabbit muscle can be loaded with cholesterol to at least 20 mol% with respect to endogenous sarcoplasmic-reticulum phospholipid without effect on the ATPase activity at 32 degrees C. This applies both to sarcoplasmic-reticulum vesicles in which the ATPase activity is stably coupled to Ca2+ accumulation, and to sarcoplasmic-reticulum vesicles in which the sarcoplasmic-reticulum ATPase is activated severalfold by fully uncoupling the enzyme from net Ca2+ accumulation. Since the incorporation of cholesterol causes a large decrease in fluidity of sarcoplasmic-reticulum phospholipid bilayer, these results for sarcoplasmic reticulum raise the more general question of whether bilayer fluidity is important in modulating the function of membrane proteins under physiological conditions as is widely assumed, or whether the function of membrane proteins may be effectively buffered under normal operating conditions against changes in bilayer fluidity due to extraneous agents.
来自兔肌肉的肌浆网囊泡可加载胆固醇，相对于内源性肌浆网磷脂，胆固醇含量至少可达20摩尔%，且在32摄氏度时对ATP酶活性无影响。这适用于ATP酶活性与Ca2+积累稳定偶联的肌浆网囊泡，也适用于通过使肌浆网ATP酶与净Ca2+积累完全解偶联而使其活性提高数倍的肌浆网囊泡。由于胆固醇的掺入导致肌浆网磷脂双层的流动性大幅降低，这些关于肌浆网的结果提出了一个更普遍的问题，即双层流动性在生理条件下调节膜蛋白功能时是否如广泛假设的那样重要，或者膜蛋白的功能在正常操作条件下是否可以有效地缓冲由于外来因素引起的双层流动性变化。
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