Effects of lung surfactant proteolipid SP-C on the organization of model membrane lipids: a fluorescence study.
Lipid-protein interactions of pulmonary surfactant-associated protein SP-C in model DPPC/DPPG and DPPC/DPPG/eggPC vesicles were studied using steady-state and time-resolved fluorescence measurements of two fluorescent phospholipid probes, NBD-PC and NBD-PG. These fluorescent probes were utilized to determine SP-C-induced lipid perturbations near the bilayer surface, and to investigate possible lipid headgroup-specific interactions of SP-C. The presence of SP-C in DPPC/DPPG membrane vesicles resulted in (1) a dramatic increase in steady-state anisotropy of NBD-PC and NBD-PG at gel phase temperatures, (2) a broadening of the gel-fluid phase transition, (3) a decrease in self-quenching of NBD-PC and NBD-PG probes, and (4) a slight increase in steady-state anisotropy of NBD-PG at fluid phase temperatures. Time-resolved measurements, as well as steady-state intensity measurements indicate that incorporation of SP-C into DPPC/DPPG or DPPC/DPPG/eggPC vesicles results in a increase in the fraction of the long-lifetime species of NBD-PC. The results presented here indicate that SP-C orders the membrane bilayer surface, disrupts acyl chain packing, and may increase the lateral pressure within the bilayer.
Horowitz
A D
AD
Division of Pulmonary Biology, Children's Hospital Medical Center, Cincinnati, OH 45229-2899.
Elledge
B
B
Whitsett
J A
JA
Baatz
J E
JE
D000818:Animals; D002417:Cattle; D005454:Fluorescence Polarization; D005456:Fluorescent Dyes; D008563:Membrane Lipids / Q000378:metabolism*; D011510:Proteolipids / Q000378:metabolism*; D011663:Pulmonary Surfactants / Q000378:metabolism*; D013696:Temperature
D005456:Fluorescent Dyes; D008563:Membrane Lipids; D011510:Proteolipids; D011663:Pulmonary Surfactants