title: Interaction of pulmonary surfactant protein SP-A with DPPC/egg-PG bilayers.
abstract: In the mixture of lipids and proteins which comprise pulmonary surfactant, the dominant protein by mass is surfactant protein A (SP-A), a hydrophilic glycoprotein. SP-A forms octadecamers that interact with phospholipid bilayer surfaces in the presence of calcium. Deuterium NMR was used to characterize the perturbation by SP-A, in the presence of 5 mM Ca(2+), of dipalmitoyl phosphatidylcholine (DPPC) properties in DPPC/egg-PG (7:3) bilayers. Effects of SP-A were uniformly distributed over the observed DPPC population. SP-A reduced DPPC chain orientational order significantly in the gel phase but only slightly in the liquid-crystalline phase. Quadrupole echo decay times for DPPC chain deuterons were sensitive to SP-A in the liquid-crystalline mixture but not in the gel phase. SP-A reduced quadrupole splittings of DPPC choline beta-deuterons but had little effect on choline alpha-deuteron splittings. The observed effects of SP-A on DPPC/egg-PG bilayer properties differ from those of the hydrophobic surfactant proteins SP-B and SP-C. This is consistent with the expectation that SP-A interacts primarily at bilayer surfaces.
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D001665:Binding Sites; D004531:Eggs; D008051:Lipid Bilayers / Q000737:chemistry*; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D008560:Membrane Fluidity; D008567:Membranes, Artificial; D008968:Molecular Conformation; D010715:Phosphatidylglycerols / Q000737:chemistry*; D011485:Protein Binding; D037662:Pulmonary Surfactant-Associated Protein A / Q000737:chemistry*; D013696:Temperature
chemical_list: D008051:Lipid Bilayers; D046911:Macromolecular Substances; D008567:Membranes, Artificial; D010715:Phosphatidylglycerols; D037662:Pulmonary Surfactant-Associated Protein A; D015060:1,2-Dipalmitoylphosphatidylcholine