Exclusion of SP-C, but not SP-B, by gel phase palmitoyl lipids.
The interactions of the hydrophobic pulmonary surfactant proteins, SP-C and SP-B, with lipid bilayers were assessed by fluorescence energy transfer. SP-C and SP-B were labeled with the fluorescent probe, succinimidyl nitrobenzoxadiazolyl amino hexanoate (NBD). Fluorescence energy transfer from NBD-SP-C and NBD-SP-B to four distinct indocarbocyanine probes (CnDiI) was utilized to determine the association of the surfactant proteins with various lipid acyl chains. In lipid mixtures including DPPC and DPPG, SP-C was associated with shorter chain and unsaturated lipids below the bulk lipid phase transition. Longer chain saturated CnDiI were excluded from SP-C aggregates. In contrast, SP-B demonstrated little acyl chain preference. The association of SP-C with shorter chain and unsaturated lipids below the bulk phase transition is interpreted to arise from a mismatch in the length of the hydrophobic region of the SP-C alpha-helix relative to the length of the hydrophobic region of dipalmitoyl lipids in the gel phase.
Horowitz
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Division of Pulmonary Biology, TCHRF 4024, Children's Hospital Medical Center, Cincinnati, Ohio 45229-3039, USA.
D000818:Animals; D002417:Cattle; D005456:Fluorescent Dyes; D008051:Lipid Bilayers / Q000737:chemistry*; D008168:Lung / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry*; D011510:Proteolipids / Q000737:chemistry*; D011663:Pulmonary Surfactants / Q000737:chemistry*; D013696:Temperature
D005456:Fluorescent Dyes; D008051:Lipid Bilayers; D010743:Phospholipids; D011510:Proteolipids; D011663:Pulmonary Surfactants