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首页> 外文期刊>Biochemistry >Effects of the core lipid on the energetics of binding of ApoA-I to model lipoprotein particles of different sizes
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Effects of the core lipid on the energetics of binding of ApoA-I to model lipoprotein particles of different sizes

机译：核心脂质对ApoA-I与不同大小的模型脂蛋白颗粒结合的能量的影响

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Interaction of apolipoproteins (apo) with lipid surfaces plays crucial roles in lipoprotein metabolism and cholesterol homeostasis. To elucidate the thermodynamics of binding of apoA-I to lipid, we used lipid emulsions composed of triolein (TO) and egg phosphatidylcholine (PC) as lipoprotein models. Determination of the level of binding of wild-type (WT) apoA-I and some deletion mutants to large (120 nm diameter; LEM) and small (35 nm diameter; SEM) emulsions indicated that N-terminal (residues 44-65) and C-terminal (residues 190-243 and 223-243) deletions have large effects on lipid interaction, whereas deletion of the central region (residues 123-166) has little effect. Substitution of amino acids at either L230 or L230, L233, and Y236 with proline residues also decreases the level of binding, indicating that an a-helix conformation in this C-terminal region is required for efficient lipid binding. Calorimetry showed that binding of WT apoA-I to SEM generates endothermic heat (Delta H similar to 30 kcal/mol) in contrast to the exothermic heat (ca. -85 kcal/mol) generated upon binding to LEM and egg PC small unilamellar vesicles (SUV). This exothermic heat arises from an similar to 25 % increase in a-helix content, and it drives the binding of apoA-I to LEM and SUV. There is a similar increase in cc-helix content of apoA-I upon binding to either SEM or SUV, but the binding of apoA-I to SEM is an entropy-driven process. These results suggest that the presence of a core triglyceride modifies the highly curved SEM surface packing and thereby the thermodynamics of apoA-I binding in a manner that compensates for the exothermic heat generated by a-helix formation.
机译：载脂蛋白（apo）与脂质表面的相互作用在脂蛋白代谢和胆固醇稳态中起着关键作用。为了阐明apoA-I与脂质结合的热力学，我们使用由三油精（TO）和卵磷脂酰胆碱（PC）组成的脂质乳剂作为脂蛋白模型。确定野生型（WT）apoA-I和一些缺失突变体与大（120 nm直径; LEM）和小（35 nm直径; SEM）乳剂的结合水平表明N末端（残基44-65） C和C末端（残基190-243和223-243）的缺失对脂质相互作用具有很大的影响，而中央区域（残基123-166）的缺失几乎没有影响。 L230或L230，L233和Y236上的脯氨酸残基取代氨基酸也降低了结合水平，表明有效的脂质结合需要该C端区域的a-螺旋构象。量热法表明，WT apoA-I与SEM的结合会产生吸热（ΔH约为30 kcal / mol），而与LEM和卵PC小单层囊泡结合时会产生放热（约-85 kcal / mol）。 （SUV）。这种放热是由α-螺旋含量增加约25％引起的，它驱使apoA-I与LEM和SUV结合。与SEM或SUV结合后，apoA-1的cc螺旋含量也有类似的增加，但是apoA-1与SEM的结合是一个熵驱动的过程。这些结果表明，核心甘油三酸酯的存在改变了高度弯曲的SEM表面堆积，从而改变了apoA-I结合的热力学，从而补偿了由α-螺旋形成所产生的放热。

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