EFFECTS OF A SURFACTANT-ASSOCIATED PROTEIN AND CALCIUM-IONS ON THE STRUCTURE AND SURFACE-ACTIVITY OF LUNG SURFACTANT LIPIDS
EFFECTS OF A SURFACTANT-ASSOCIATED PROTEIN AND CALCIUM-IONS ON THE STRUCTURE AND SURFACE-ACTIVITY OF LUNG SURFACTANT LIPIDS
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DOI：
10.1021/bi00322a026
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发表时间：
1985-01-01
期刊：
影响因子：
2.9
通讯作者：
HAMILTON, RL
中科院分区：
文献类型：
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作者：
HAWGOOD, S;BENSON, BJ;HAMILTON, RL
先前的研究表明，肺特异性蛋白质与表面活性剂脂质相关，特别是被称为管状髓磷脂的高表面活性亚组分。分离出分子量为 36,000、32,000 和 28,000 的表面活性剂相关蛋白复合物，并用制备为小单层脂质体的无蛋白肺表面活性剂脂质重新组装。通过浊度变化和 EM 跟踪脂质分散状态，并跟踪表面活性剂脂质在 37°C 下从水性底相形成表面膜的能力，研究了二价阳离子对该蛋白质-脂质混合物的结构和表面活性的影响。 C. 蛋白质复合物显着增加了 Ca2+ 诱导的表面活性剂-脂质聚集的速率。 EM 证明小单层脂质体（中位直径 440 ANG）转化为大聚集体。蛋白质复合物将快速脂质聚集所需的阈值 Ca2+ 浓度从 13 mM 降低至 0.5 mM。如果 Mg2+ 是唯一存在的二价阳离子，则不会发生这种蛋白质促进的脂质聚集。类似地，5 mM Ca2+ 但不是 5 mM Mg2+ 提高了蛋白质-脂质混合物在 37°C 形成表面膜的能力。 C. 不含蛋白质的表面活性剂脂质通过 20 mM Ca2+ 或 20 mM Mg2+ 的广泛聚集不会促进快速表面膜形成。这些结果进一步证明，特定的 Ca2+-蛋白质-脂质相互作用对于确定细胞外肺表面活性剂组分的结构和功能非常重要。
Previous studies have demonstrated that lung-specific proteins are associated with surfactant lipids, particularly the highly surface active subfraction known as tubular myelin. A surfactant-associated protein complex with MW components of 36,000, 32,000 and 28,000 was isolated and reassembled with protein-free lung surfactant lipids prepared as small unilamellar liposomes. The effects of divalent cations on the structure and surface activity of this protein-lipid mixture were investigated by following the state of lipid dispersion by changes in turbidity and by EM and following the ability of the surfactant lipids to form a surface film from an aqueous subphase at 37.degree. C. The protein complex markedly increased the rate of Ca2+-induced surfactant-lipid aggregation. EM demonstrated transformation of the small unilamellar liposomes (median diameter 440 .ANG.) into large aggregates. The threshold Ca2+ concentration required for rapid lipid aggregation was reduced from 13 to 0.5 mM by the protein complex. This protein-facilitated lipid aggregation did not occur if Mg2+ was the only divalent cation present. Similary, 5 mM Ca2+ but not 5 mM Mg2+ improved the ability of the protein-lipid mixture to form a surface film at 37.degree. C. Extensive aggregation of the surfactant lipids without protein by 20 mM Ca2+ or 20 mM Mg2+ did not promote rapid surface film formation. These results add to the growing evidence that specific Ca2+-protein-lipid interactions are important in determining the structure and function of extracellular lung surfactant fractions.