Qanbar R, Cheng S, Possmayer F, Schürch S
Department of Biochemistry, University of Western Ontario, London, Canada.
Am J Physiol. 1996 Oct;271(4 Pt 1):L572-80. doi: 10.1152/ajplung.1996.271.4.L572.
The effect of palmitoylation of pulmonary surfactant-associated protein C (SP-C) on the surface activity of phospholipid mixtures of dipalmitoylphosphatidylcholine and phosphatidylglycerol was studied. Phospholipids reconstituted with palmitoylated or depalmitoylated bovine SP-C were examined at neutral and acidic pH using a captive bubble surfactometer. At low pH, effective lipid adsorption and near zero surface tensions upon compression were obtained even with protein-free samples. At physiological pH, only SP-C-containing samples achieved such properties. Lipid adsorption was decreased by prior SP-C depalmitoylation. Bubbles with palmitoylated SP-C were more mechanically stable and required less compression to reach low surface tensions. Subphase depletion experiments showed that dynamically cycled surface layers containing palmitoylated SP-C maintained their surface activity after subphase lipid depletion. In contrast, surface activity was rapidly lost where depalmitoylated SP-C or SP-B was included. Our results indicate that although SP-C palmitoylation has little effect on its ability to enhance lipid adsorption and surface tension reduction, it greatly enhances lipid respreading and film stability and is therefore important for surfactant function.
研究了肺表面活性物质相关蛋白C（SP-C）的棕榈酰化对二棕榈酰磷脂酰胆碱和磷脂酰甘油磷脂混合物表面活性的影响。使用俘获气泡表面张力仪，在中性和酸性pH条件下检测了用棕榈酰化或去棕榈酰化牛SP-C重构的磷脂。在低pH值下，即使是无蛋白样品也能实现有效的脂质吸附和压缩时接近零的表面张力。在生理pH值下，只有含SP-C的样品具有这些特性。预先对SP-C进行去棕榈酰化会降低脂质吸附。含有棕榈酰化SP-C的气泡在机械上更稳定，达到低表面张力所需的压缩更少。亚相耗尽实验表明，含有棕榈酰化SP-C的动态循环表面层在亚相脂质耗尽后仍保持其表面活性。相比之下，当包含去棕榈酰化SP-C或SP-B时，表面活性会迅速丧失。我们的结果表明，尽管SP-C的棕榈酰化对其增强脂质吸附和降低表面张力的能力影响不大，但它大大增强了脂质再铺展和膜稳定性，因此对表面活性剂功能很重要。
