Interaction between perdeuterated dimyristoylphosphatidylcholine and low molecular weight pulmonary surfactant protein SP-C

• Published in: Biochemistry (Easton) 1990-06, Vol.29 (24), p.5807-5814
• Main Authors: Simatos, G. A, Forward, Kenneth B, Morrow, M. R, Keough, K. M. W
• Format: Article
• Language: English
• Subjects: ADSORPTION; AMINO ACID SEQUENCE; ANIMALS; BASIC BIOLOGICAL SCIENCES; BIOCHEMICAL REACTION KINETICS; Biological and medical sciences; BODY; CALORIMETRY; Calorimetry, Differential Scanning; CHROMATOGRAPHY; COMPARATIVE EVALUATIONS; DEUTERIUM; Dimyristoylphosphatidylcholine; DOMESTIC ANIMALS; ELECTROPHORESIS; ESTERS; Fundamental and applied biological sciences. Psychology; HYDROGEN ISOTOPES; Interactions. Associations; Intermolecular phenomena; ISOTOPE APPLICATIONS; ISOTOPES; KINETICS; LAVAGE; LIGHT NUCLEI; LIPIDS; Lung - analysis; LUNGS; MAGNETIC RESONANCE; Magnetic Resonance Spectroscopy; MAMMALS; Molecular biophysics; MOLECULAR STRUCTURE; MOLECULAR WEIGHT; NMR SPECTRA; NUCLEAR MAGNETIC RESONANCE; NUCLEI; ODD-ODD NUCLEI; ORGANIC COMPOUNDS; ORGANIC PHOSPHORUS COMPOUNDS; ORGANS; PHOSPHOLIPIDS; PROTEINS; Proteolipids; Pulmonary Surfactant-Associated Proteins; Pulmonary Surfactants; REACTION KINETICS; RESONANCE; RESPIRATORY SYSTEM; SEPARATION PROCESSES; SORPTION; SPECTRA; STABLE ISOTOPES; SURFACE PROPERTIES; SURFACE TENSION; SURFACTANTS; SWINE; Temperature; TRACER TECHNIQUES; VERTEBRATES 550201 > Biochemistry-- Tracer Techniques
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00476a023

A low molecular weight hydrophobic protein was isolated from porcine lung lavage fluid using silicic acid and Sephadex LH-20 chromatography. The protein migrated with an apparent molecular weight of 5000-6000 on SDS-PAGE under reducing and nonreducing conditions. Gels run under reducing conditions also showed a minor band migrating with a molecular weight of 12,000. Amino acid compositional analysis and sequencing data suggest that this protein preparation contains intact surfactant protein SP-C and about 30% of truncated SP-C (N-terminal leucine absent). The surfactant protein was combined with perdeuterated dimyristoylphosphatidylcholine (DMPC-d54) in multilamellar vesicles. The protein enhanced the rate of adsorption of the lipid at air-water interfaces. The ability of the protein to alter normal lipid organization was examined by using high-sensitivity differential scanning calorimetry (DSC) and 2H nuclear magnetic resonance spectroscopy (2H NMR). The calorimetric measurements indicated that the protein caused a decrease in the temperature maximum (Tm) and a broadening of the phase transition. At a protein concentration of 8% (w/w), the enthalpy change of transition was reduced to 4.4 kcal/mol compared to 6.3 kcal/mol determined for the pure lipid. NMR spectral moment studies indicated that protein had no effect on lipid chain order in the liquid-crystal phase but reduced orientational order in the gel phase. Two-phase coexistence in the presence of protein was observed over a small temperature range below the pure lipid transition temperature. Spin-lattice relaxation times (T1) were not substantially affected by the protein. Transverse relaxation time (T2e) studies suggest that the protein influences slow lipid motions.