Lopes C M, Louro S R
Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro, Brasil.
Biochim Biophys Acta. 1991 Dec 9;1070(2):467-73. doi: 10.1016/0005-2736(91)90088-p.
The effects of ethanol, n-butanol, n-hexanol and n-octanol on lipid-protein interactions in sarcoplasmic reticulum vesicles (SRV) are investigated using the C-14 nitroxide spin-labeled phosphatidylcholine. n-Alkanols, which activate the Ca(2+)-dependent ATPase of sarcoplasmic reticulum but decrease net Ca2+ uptake by the vesicles, are shown to affect the lipids interacting with the protein surface. Spectral analysis revealed that increasing concentrations of the alcohols progressively displace and mobilize lipids from the lipid/protein interface. For butanol, hexanol and octanol maximally activated SRV, 23 to 30% of the protein-interacting lipids are displaced. Thus, the displacement of more than 30% of the annular lipids by these alkanols cause inhibition of the enzyme. The motional properties of the labels that remain restricted by the protein surface are unaffected by the alcohols. The degree of mobilization attained by the labels displaced from the interface is much greater than that observed in alcohol-treated dispersions of extracted lipids. We propose that the alcohol molecules interfere with the protein-lipid interactions creating fluid clusters around the proteins. These fluidized regions would affect the enzyme conformation, perturbing its function. Fluidized annular lipids apparently increase the number of ion-conducting defects around the enzyme, increasing Ca2+ efflux, and thereby reducing net uptake.
使用C-14氮氧化物自旋标记的磷脂酰胆碱，研究了乙醇、正丁醇、正己醇和正辛醇对肌浆网囊泡（SRV）中脂质-蛋白质相互作用的影响。正链烷醇可激活肌浆网的Ca(2+)依赖性ATP酶，但会减少囊泡对Ca2+的净摄取，结果表明其会影响与蛋白质表面相互作用的脂质。光谱分析显示，醇浓度的增加会逐渐使脂质从脂质/蛋白质界面移位并使其移动。对于丁醇、己醇和辛醇，当SRV被最大程度激活时，23%至30%与蛋白质相互作用的脂质会被移位。因此，这些链烷醇使超过30%的环形脂质移位会导致酶受到抑制。仍受蛋白质表面限制的标记物的运动特性不受醇的影响。从界面移位的标记物所达到的移动程度远大于在醇处理的提取脂质分散体中观察到的程度。我们认为，醇分子会干扰蛋白质-脂质相互作用，在蛋白质周围形成流体簇。这些流化区域会影响酶的构象，扰乱其功能。流化的环形脂质显然会增加酶周围离子传导缺陷的数量，增加Ca2+外流，从而减少净摄取。
