Effect of cholesterol on the formation of micellar complexes between bovine A-I apolipoprotein and L-alpha-dimyristoylphosphatidylcholine.
Effect of cholesterol on the formation of micellar complexes between bovine A-I apolipoprotein and L-alpha-dimyristoylphosphatidylcholine.
复制标题
胆固醇对牛 A-I 载脂蛋白和 L-α-二肉豆蔻酰磷脂酰胆碱之间胶束复合物形成的影响。
DOI：
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发表时间：
1978
影响因子：
4.8
通讯作者：
D. Krajnovich
中科院分区：
文献类型：
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作者：
A. Jonas;D. Krajnovich
研究了牛A-I型载脂蛋白与含不同摩尔比胆固醇的二肉豆蔻酰磷脂酰胆碱超声囊泡的相互作用。通过在Sepharose 4 B柱上凝胶过滤分离在37°C下制备的复合物。化学计量，获得和固有荧光和圆二色光谱特性进行了测定纯化的复合物。通过测量溶解在复合物中的荧光亲脂性探针二苯基己三烯的荧光偏振来探测脂质结构域的流动性变化。载脂蛋白A-I从含有高达33 mol %胆固醇的二肉豆蔻酰磷脂酰胆碱囊泡形成“小”分解复合物。这些复合物具有高密度血清脂蛋白的一般大小，并且都具有相似的形状。当胆固醇含量超过37mol%时，脂囊泡与载脂蛋白没有相互作用。很可能在胆固醇含量下囊泡中发生结构变化，从而阻止复合物形成。载脂蛋白A-I与二肉豆蔻酰磷脂酰胆碱和胆固醇的所有复合物都含有相同的磷脂与蛋白质的摩尔比（95：1），但相对于母体囊泡中的脂质比，它们富含磷脂而不是胆固醇。这些结果，以及观察到含有或不含有胆固醇的复合物的蛋白质光谱特性非常相似，强烈表明与蛋白质相邻的脂质层仅为磷脂。在载脂蛋白A-I的复合物中，二肉豆蔻酰磷脂酰胆碱的流动性逐渐受到胆固醇的明显限制，这表明胆固醇在这些复合物中具有与磷脂双层相似的凝聚作用。
The interaction of bovine A-I apolipoprotein with sonicated vesicles of dimyristoylphosphatidylcholine containing various molar ratios of cholesterol was investigated in this work. Complexes prepared at 37°C were isolated by gel filtration on Sepharose 4B columns. Stoichiometries were obtained and intrinsic fluorescence and circular dichroism spectral properties were determined for the purified complexes. Fluidity changes of the lipid domains were probed by measuring the fluorescence polarization of the fluorescent lipophilic probe diphenylhexatriene dissolved in the complexes. Apolipoprotein A-I forms “small” breakdown complexes from vesicles of dimyristoylphosphatidylcholine containing up to 33 mol % cholesterol. These complexes are of the general size of high density serum lipoproteins and all have similar shapes. At cholesterol contents exceeding 37 mol %, there is no interaction of lipid vesicles with the apolipoprotein. It is likely that structural changes occur in the vesicles at this cholesterol content which prevent complex formation. All the complexes of apolipoprotein A-I with dimyristoylphosphatidylcholine and cholesterol contain the same molar ratio of phospholipid to protein (95:1), but they are enriched in phospholipid over cholesterol relative to the lipid ratios in the parent vesicles. These results, together with the observation that the protein spectral properties of complexes with or without cholesterol are very similar, strongly suggest that the lipid layer adjacent to the protein is exclusively phospholipid. The mobility of dimyristoylphosphatidylcholine in the complexes with apolipoprotein A-I is progressively and markedly restricted by the presence of cholesterol, indicating that cholesterol has a similar condensing effect in these complexes as in phospbolipid bilayers.