Role of the palmitoylation of surfactant-associated protein C in surfactant film formation and stability.
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.
Department of Biochemistry, University of Western Ontario, London, Canada.
R
R
Qanbar
S
S
Cheng
F
F
Possmayer
S
S
Schürch
D015060:1,2-Dipalmitoylphosphatidylcholine; D000215:Acylation; D000327:Adsorption; D000818:Animals; D002417:Cattle; D006863:Hydrogen-Ion Concentration; D010168:Palmitates; D010507:Periodicity; D011510:Proteolipids; D011663:Pulmonary Surfactants; D013499:Surface Properties; D013500:Surface Tension
D010168:Palmitates; D011510:Proteolipids; D011663:Pulmonary Surfactants; D015060:1,2-Dipalmitoylphosphatidylcholine