Modulation of metarhodopsin formation by cholesterol-induced ordering of bilayer lipids.
Modulation of metarhodopsin formation by cholesterol-induced ordering of bilayer lipids.
复制标题
通过胆固醇诱导的双层脂质排序调节变视紫红质的形成。
DOI：
10.1021/bi00491a007
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发表时间：
1990
期刊：
影响因子：
2.9
通讯作者：
B. Litman
中科院分区：
文献类型：
--
作者：
D. C. Mitchell;Martin Straume;James L. Miller;B. Litman
脂质排序对后视紫红质II （meta II）形成的动力学和程度的影响进行了评估，将牛视紫红质重组为含有0、15%和30% mol%胆固醇的磷脂酰胆碱囊泡。分支meta - II模型中后视紫红质I （meta - I）与meta - II两种不同的动力学形式之间建立动态平衡的速率[meta - ifast和meta - ilow]；Straume， M., Mitchell， D. C., Miller， J. L., & Litman， B. J.(1990)[生物化学]（本期的前一篇论文）是从在不同温度下这些囊泡系统中视紫红质光解的动力学测量中得出的。平衡态中元I与元I总平衡常数Keq的值是由模型相关的速率常数计算得出的，与快速获得的吸光度光谱结果相当。30mol %胆固醇的存在使Keq在10到37摄氏度之间降低了大约50%。对模型相关参数的分析表明，胆固醇通过增加H提高了相对于元I的元I的自由能，而通过使相对于元I的元I的元S相对于元I降低了正，从而提高了相对于元I的元I的自由能。温度和胆固醇对Keq的降低与反映双分子层疏水核心中分子运动的自由体积的参数直接相关[Straume， M., & Litman, b.j. (1988) Biochemistry 27, 7723-7733]。（摘要删节250字）
The effect of lipid ordering on the kinetics and extent of metarhodopsin II (meta II) formation was evaluated in bovine rhodopsin which had been reconstituted into phosphatidylcholine vesicles containing 0, 15, and 30 mol% cholesterol. The rate of establishment of the dynamic equilibrium between metarhodopsin I (meta I) and the two kinetically distinguished forms of meta II in the branched meta II model [meta IIfast and meta IIslow; Straume, M., Mitchell, D. C., Miller, J. L., & Litman, B. J. (1990) Biochemistry (preceding paper in this issue)] is derived from kinetic measurements of rhodopsin photolysis in these vesicle systems at several temperatures. Values of the meta I in equilibrium with meta IItotal equilibrium constant, Keq, are calculated from the derived model-dependent rate constants, and are shown to be equivalent to those derived from rapidly acquired absorbance spectra. The presence of 30 mol% cholesterol reduces Keq by approximately 50% between 10 and 37 degrees C. Analysis of the model-dependent parameters in terms of delta H and delta S reveals that cholesterol raises the free energy of meta IIslow, relative to meta I, by increasing delta H whereas it raises the relative free energy of meta IIfast by making delta S meta IIfast relative to meta I less positive. The reduction in Keq by both temperature and cholesterol is found to be directly correlated with a parameter that reflects the free volume available for molecular motion in the hydrophobic core of the bilayer [Straume, M., & Litman, B. J. (1988) Biochemistry 27, 7723-7733].(ABSTRACT TRUNCATED AT 250 WORDS)