Effects of surfactant-associated protein SP-B synthetic analogs on the structure and surface activity of model membrane bilayers

Baatz, John E.; Sarin, Viren; Absolom, D. R.; Baxter, Connie; Whitsett, Jeffrey A.

doi:10.1016/0009-3084(91)90039-e

Cited by 58 publications

(45 citation statements)

References 23 publications

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“…SP-B can order the head-group region of lipid bilayers and increase the gel-to-liquid crystal transition temperatures of fluid phospholipids (1,2,30,53,54). SP-B also broadens phase transition width, indicating an ability to disrupt or reduce order in at least a portion of the bilayer (1,2,23,24,30,43). The extensive molecular biophysical interactions between SP-B and phospholipids support a crucial role for this apoprotein in surfactant biophysical function consistent with the activity findings here.…”

Section: Discussionsupporting

confidence: 82%

“…Due to its overall amphipathic structure, SP-B likely occupies a relatively peripheral position in phospholipid bilayers where it can interact with both head groups and hydrophobic chains (1,10,40,42,43,53). SP-B can order the head-group region of lipid bilayers and increase the gel-to-liquid crystal transition temperatures of fluid phospholipids (1,2,30,53,54). SP-B also broadens phase transition width, indicating an ability to disrupt or reduce order in at least a portion of the bilayer (1,2,23,24,30,43).…”

Section: Discussionmentioning

confidence: 99%

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Content-dependent activity of lung surfactant protein B in mixtures with lipids

Wang

Baatz

Holm

et al. 2002

American Journal of Physiology-Lung Cellular and Molecular Phys

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The content-dependent activity of surfactant protein (SP)-B was studied in mixtures with dipalmitoyl phosphatidylcholine (DPPC), synthetic lipids (SL), and purified phospholipids (PPL) from calf lung surfactant extract (CLSE). At fixed SP-B content, adsorption and dynamic surface tension lowering were ordered as PPL/SP-B ≈ SL/SP-B > DPPC/SP-B. All mixtures were similar in having increased surface activity as SP-B content was incrementally raised from 0.05 to 0.75% by weight. SP-B had small but measurable effects on interfacial properties even at very low levels ≤0.1% by weight. PPL/SP-B (0.75%) had the highest adsorption and dynamic surface activity, approaching the behavior of CLSE. All mixtures containing 0.75% SP-B reached minimum surface tensions <1 mN/m in pulsating bubble studies at low phospholipid concentration (1 mg/ml). Mixtures of PPL or SL with SP-B (0.5%) also had minimum surface tensions <1 mN/m at 1 mg/ml, whereas DPPC/SP-B (0.5%) reached <1 mN/m at 2.5 mg/ml. Physiological activity also was strongly dependent on SP-B content. The ability of instilled SL/SP-B mixtures to improve surfactant-deficient pressure-volume mechanics in excised lavaged rat lungs increased as SP-B content was raised from 0.1 to 0.75% by weight. This study emphasizes the crucial functional activity of SP-B in lung surfactants. Significant differences in SP-B content between exogenous surfactants used to treat respiratory disease could be associated with substantial activity variations.

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Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Content-dependent activity of lung surfactant protein B in mixtures with lipids

Wang

Baatz

Holm

et al. 2002

American Journal of Physiology-Lung Cellular and Molecular Phys

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“…The lack of changes, within experimental error, in the fluorescence emission of DPH with increasing amounts of peptide (data not shown), allows us to infer that KL 4 enhances the lipid order of DPPC ⁄ POPG, DPPC ⁄ POPG ⁄ PA and DPPC ⁄ POPC ⁄ PA membranes. These results are consistent with the ordering effect of SP-B and related peptides on the polar surface of DPPC ⁄ PG vesicles [23,24].…”

Section: Effect Of Kl 4 On the Lipid Order Of Surfactant-like Membranessupporting

confidence: 89%

Physical properties and surface activity of surfactant‐like membranes containing the cationic and hydrophobic peptide KL₄

et al. 2006

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Surfactant-like membranes containing the 21-residue peptide KLLLL-KLLLLKLLLLKLLLLK (KL 4 ), have been clinically tested as a therapeutic agent for respiratory distress syndrome in premature infants. The aims of this study were to investigate the interactions between the KL 4 peptide and lipid bilayers, and the role of both the lipid composition and KL 4 structure on the surface adsorption activity of KL 4 -containing membranes. We used bilayers of three-component systems [1,2-dipalmitoyl-phosphatidylcholine ⁄ 1-palmitoyl-2-oleoyl-phosphatidylglycerol ⁄ palmitic acid (DPPC ⁄ POPG ⁄ PA) and DPPC ⁄ 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) ⁄ PA] and binary lipid mixtures of DPPC ⁄ POPG and DPPC ⁄ PA to examine the specific interaction of KL 4 with POPG and PA. We found that, at low peptide concentrations, KL 4 adopted a predominantly a-helical secondary structure in POPG-or POPC-containing membranes, and a b-sheet structure in DPPC ⁄ PA vesicles. As the concentration of the peptide increased, KL 4 interconverted to a b-sheet structure in DPPC ⁄ POPG ⁄ PA or DPPC ⁄ POPC ⁄ PA vesicles. Ca 2+ favored a«b interconversion. This conformational flexibility of KL 4 did not influence the surface adsorption activity of KL 4 -containing vesicles. KL 4 showed a concentration-dependent ordering effect on POPG-and POPC-containing membranes, which could be linked to its surface activity. In addition, we found that the physical state of the membrane had a critical role in the surface adsorption process. Our results indicate that the most rapid surface adsorption takes place with vesicles showing well-defined solid ⁄ fluid phase co-existence at temperatures below their gel to fluid phase transition temperature, such as those of DPPC ⁄ POPG ⁄ PA and DPPC ⁄ POPC ⁄ PA. In contrast, more fluid (DPPC ⁄ POPG) or excessively rigid (DPPC ⁄ PA) KL 4 -containing membranes fail in their ability to adsorb rapidly onto and spread at the airwater interface.Abbreviations Bodipy-PC, 2-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-pentanoyl)-1-hexadecanoyl-sn-glycero-3-phosphocholine; DPH, 1,6-diphenyl-1,3,5-hexatriene; DPPC, 1,2-dipalmitoyl-phosphatidylcholine; DSC, differential scanning calorimetry; GUV, giant unilamellar vesicle; PA, palmitic acid; PC, phosphatidylcholine; POPC, 1-palmitoyl-2-oleoyl-phosphatidylcholine; POPG, 1-palmitoyl-2-oleoyl-phosphatidylglycerol; RDS, respiratory distress syndrome; SP-B, surfactant protein B; SP-C, surfactant protein C; T m , gel to fluid phase transition temperature.

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“…Recent studies have indicated that in alveolar proteinosis in which an abnormal form of SP-A is produced (Hattori et al, 1996) and in SP-A gene ablation or knockout mice (Korfhagen et al, 1996), tubular myelin is absent in surfactant. SP-B is a highly conserved, hydrophobic 17-kDa dimer which can fuse lipid bilayer membranes containing acidic lipids (Baatz et al, 1991;Poulain et al, 1996). In contrast, SP-A is a water-soluble 650-kDa, octadecameric glycoprotein that causes extensive aggregation of DPPC liposomal vesicles (Casals et al, 1993;Poulain et al, 1992).…”

Section: Introductionmentioning

confidence: 99%

Correlated Atomic Force and Transmission Electron Microscopy of Nanotubular Structures in Pulmonary Surfactant

Nag

Munro

Hearn

et al. 1999

Journal of Structural Biology

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Pulmonary surfactant stabilizes the lung by reducing surface tension at the air-water interface of the alveoli. Surfactant is present in the lung in a number of morphological forms, including tubular myelin (TM). TM is composed of unusual 40 ؋ 40 nm square elongated proteolipid tubes. Atomic force microscopy (AFM) was performed on polymerembedded Lowicryl and London Resin-White (LRWhite) unstained thin sections. AFM was used in imaging regions of the sections where TM was detected by transmission electron microscopy (EM) of corresponding stained sections. Tapping-and contact-mode AFM imaging of the unstained sections containing TM indicated a highly heterogeneous surface topography with height variations ranging from 10 to 100 nm. In tapping-mode AFM, tubular myelin was seen as hemispherical protrusions of 30-70 nm in diameter, with vertical dimensions of 5-8 nm. In contact-mode AFM and with phase imaging using a sharper (G10 nm nominal radius) probe, square open-ended tubes which resembled typical electron micrographs of such regions were observed. The cross-hatch structures observed inside the tubes using EM were not observed using AFM, although certain multilobe structures and topographic heterogeneity were detected inside some tubes. Other regions of multilamellar bodies and some regions where such bilayer lamella appear to fuse with the tubes were found in association with TM using AFM. EM of acetone-delipidated tubes in LR-White revealed rectangular tubular cores containing cross-hatched structures, presumably protein skeletons. AFM surface topography of these regions showed hollow depressions at positions at which the protein was anticipated instead of the protrusions seen in the lipid-containing sections. Gold-labeled antibody to surfactant protein A was found associated somewhat randomly within the regions containing the protein skeletons. The topography of the gold particles was observed as sharp peaks in contact-mode AFM. This study suggests a method for unambiguous detection of threedimensional nanotubes present in low abundance in a biological macromolecular complex. Only limited detection of proteins and lipids in surfaces of embedded tubular myelin was possible. EM and AFM imaging of such unusual biological structures may suggest unique lipid-protein associations and arrangements in three dimensions. Academic Press

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Effects of surfactant-associated protein SP-B synthetic analogs on the structure and surface activity of model membrane bilayers

Cited by 58 publications

References 23 publications

Content-dependent activity of lung surfactant protein B in mixtures with lipids

Content-dependent activity of lung surfactant protein B in mixtures with lipids

Physical properties and surface activity of surfactant‐like membranes containing the cationic and hydrophobic peptide KL₄

Correlated Atomic Force and Transmission Electron Microscopy of Nanotubular Structures in Pulmonary Surfactant

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Effects of surfactant-associated protein SP-B synthetic analogs on the structure and surface activity of model membrane bilayers

Cited by 58 publications

References 23 publications

Content-dependent activity of lung surfactant protein B in mixtures with lipids

Content-dependent activity of lung surfactant protein B in mixtures with lipids

Physical properties and surface activity of surfactant‐like membranes containing the cationic and hydrophobic peptide KL4

Correlated Atomic Force and Transmission Electron Microscopy of Nanotubular Structures in Pulmonary Surfactant

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Physical properties and surface activity of surfactant‐like membranes containing the cationic and hydrophobic peptide KL₄