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Topographical organization of the n-terminal segment of lung pulmonary surfactant protein b (SP-B 1-25) in a phospholipid bilayer as determined by fluorescence quenching.
Wang Y; Rao MK; Demchuk E
Biophys J 2003 Feb; 84(2)(Part 2):54a
The location and depth of each residue on the phospholid bilayer (PB) was determined by fluorescence quenching with synthesized single residue substituted peptides that were rconstituted into DPPC-enriched liposomes. The single residue subsitutions in peptides were either aspartate or tryptophan. Asparate was subsequently labeled with the NCD-4 flurophore. The spin-labeled compounds, 5-DSA, 7-DSA, 12-DSA, CAT-16, and CAT-1 were used in quenching experiments. Our observations indicated that residues 1-6 are located at the surface of PB; residues 7-9 are embedded in PB; residues 10-22 are involved in an amphipathic alpha-helix with its axis somewhat parallel to the surface of PB; residues 23-25 reside at the surface. Effects of the inter-molecule disulfide bond formation in the SP-B 1-25 dimer were also investigated. The data suggest that hydrophobic sides of the amphipathic helixes face each other forming a hydrophobic domain. The environment-sepcific conformational liability in this hydrophobic domain may explain the key impact of SP-B on the phospholipid transport from bi- to mono-layer and in modulating the cell inflammatory response during the respiratory distress syndrome conditions.
Lung-function; Pulmonary-function; Pulmonary-system; Peptides; Lipids; Phospholipids; Cellular-reactions; Cellular-function
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