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Title: Pulmonary surfactant protein A (SP-A) specifically binds dipalmitoylphosphatidylcholine

Phospholipids are the major components of pulmonary surfactant. Dipalmitoylphosphatidylcholine is believed to be especially essential for the surfactant function of reducing the surface tension at the air-liquid interface. Surfactant protein A (SP-A) with a reduced denatured molecular mass of 26-38 kDa, characterized by a collagen-like structure and N-linked glycosylation, interacts strongly with a mixture of surfactant-like phospholipids. In the present study the direct binding of SP-A to phospholipids on a thin layer chromatogram was visualized using 125I-SP-A as a probe, so that the phospholipid specificities of SP-A binding and the structural requirements of SP-A and phospholipids for the binding could be examined. Although 125I-SP-A bound phosphatidylcholine and sphingomyeline, it was especially strong in binding dipalmitoylphosphatidylcholine, but failed to bind phosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine, and phosphatidylserine. Labeled SP-A also exhibited strong binding to distearoylphosphatidylcholine, but weak binding to dimyristoyl-, 1-palmitoyl-2-linoleoyl-, and dilinoleoylphosphatidylcholine. Unlabeled SP-A readily competed with labeled SP-A for phospholipid binding. SP-A strongly bound dipalmitoylglycerol produced by phospholipase C treatment of dipalmitoylphosphatidylcholine, but not palmitic acid. This protein also failed to bind lysophosphatidylcholine produced by phospholipase A2 treatment of dipalmitoylphosphatidylcholine. 125I-SP-A shows almost no binding to dipalmitoylphosphatidylglycerol and dipalmitoylphosphatidylethanolamine. The addition of 10 mM EGTA into the binding buffer reduced muchmore » of the 125I-SP-A binding to phospholipids. Excess deglycosylated SP-A competed with labeled SP-A for binding to dipalmitoylphosphatidylcholine, but the excess collagenase-resistant fragment of SP-A failed.« less
Authors:
;  [1]
  1. (Sapporo Medical College (Japan))
Publication Date:
OSTI Identifier:
6057029
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Biological Chemistry; (USA); Journal Volume: 266:5
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; PROTEINS; BIOCHEMICAL REACTION KINETICS; CARBOXYLIC ACIDS; CHEMICAL COMPOSITION; CPB; IODINE 125; LIPASES; LUNGS; PHOSPHOLIPIDS; RATS; TRACER TECHNIQUES; ANIMALS; BETA DECAY RADIOISOTOPES; BODY; CARBOXYLESTERASES; DAYS LIVING RADIOISOTOPES; ELECTRON CAPTURE RADIOISOTOPES; ENZYMES; ESTERASES; ESTERS; HYDROLASES; INTERMEDIATE MASS NUCLEI; IODINE ISOTOPES; ISOTOPE APPLICATIONS; ISOTOPES; KINETICS; LIPIDS; MAMMALS; NUCLEI; ODD-EVEN NUCLEI; ORGANIC ACIDS; ORGANIC COMPOUNDS; ORGANIC PHOSPHORUS COMPOUNDS; ORGANS; RADIOISOTOPES; REACTION KINETICS; RESPIRATORY SYSTEM; RODENTS; VERTEBRATES 550201* -- Biochemistry-- Tracer Techniques