Differential Effects of the Hydrophobic Surfactant Proteins on the Formation of Inverse Bicontinuous Cubic Phases

Chavarha, Mariya; Loney, Ryan W.; Kumar, Kamlesh; Rananavare, Shankar B.; Hall, Stephen B.

doi:10.1021/la3025364

Cited by 22 publications

(20 citation statements)

References 72 publications

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“…The changes demonstrated here presumably reflect mainly the influence of the proteins on the phospholipid acyl chains. SP-C, with a hydrophobic sequence appropriate to span a bilayer (53), has much less ability than SP-B to affect adsorption (54) or induce formation of Q II phases (36). Our results imply that SP-B inserts deep within the hydrophobic portions of the phospholipid leaflet.…”

Section: Proteins Induce Negative Curvaturementioning

confidence: 82%

“…Extracted calf surfactant, obtained from Dr. Edmund Egan (ONY, Amherst, NY), provided the source of the hydrophobic surfactant proteins, which were separated in their physiological ratio from the surfactant lipids by gel permeation chromatography (33)(34)(35). SP-B and SP-C isolated by this procedure have the expected characteristics (36,37). SP-B migrates electrophoretically on gels as a reducible homodimer of monomers containing 79 amino acids.…”

Section: Methodsmentioning

confidence: 94%

“…The conversion by the proteins of lamellar 1-palmitoyl-2-oleoyl phosphatidylethanolamine to cubic phases (36,37) suggests an effect on curvature. The changes in the DOPE:DOPG cylinders (22) were relatively small, but they demonstrated a dose-related effect of the proteins on curvature.…”

Section: Proteins Induce Negative Curvaturementioning

confidence: 99%

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Hydrophobic Surfactant Proteins Strongly Induce Negative Curvature

Chavarha

Loney

Rananavare

et al. 2015

Biophysical Journal

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The hydrophobic surfactant proteins SP-B and SP-C greatly accelerate the adsorption of vesicles containing the surfactant lipids to form a film that lowers the surface tension of the air/water interface in the lungs. Pulmonary surfactant enters the interface by a process analogous to the fusion of two vesicles. As with fusion, several factors affect adsorption according to how they alter the curvature of lipid leaflets, suggesting that adsorption proceeds via a rate-limiting structure with negative curvature, in which the hydrophilic face of the phospholipid leaflets is concave. In the studies reported here, we tested whether the surfactant proteins might promote adsorption by inducing lipids to adopt a more negative curvature, closer to the configuration of the hypothetical intermediate. Our experiments used x-ray diffraction to determine how the proteins in their physiological ratio affect the radius of cylindrical monolayers in the negatively curved, inverse hexagonal phase. With binary mixtures of dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC), the proteins produced a dose-related effect on curvature that depended on the phospholipid composition. With DOPE alone, the proteins produced no change. With an increasing mol fraction of DOPC, the response to the proteins increased, reaching a maximum 50% reduction in cylindrical radius at 5% (w/w) protein. This change represented a doubling of curvature at the outer cylindrical surface. The change in spontaneous curvature, defined at approximately the level of the glycerol group, would be greater. Analysis of the results in terms of a Langmuir model for binding to a surface suggests that the effect of the lipids is consistent with a change in the maximum binding capacity. Our findings show that surfactant proteins can promote negative curvature, and support the possibility that they facilitate adsorption by that mechanism.

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Section: Proteins Induce Negative Curvaturementioning

confidence: 82%

Section: Methodsmentioning

confidence: 94%

See 1 more Smart Citation

Hydrophobic Surfactant Proteins Strongly Induce Negative Curvature

Chavarha

Loney

Rananavare

et al. 2015

Biophysical Journal

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“…One approach to studying the way in which hydrophobic lung surfactant proteins modify lipid organization has been to use lipids, like 1-palmitoyl-2-oleoyl phosphatidylethanolamine (POPE), with a propensity to form non-bilayer phases with highly curved surfaces [5], [28], [29]. In the absence of peptide, bilayers of POPE undergo a lamellar to inverted hexagonal phase transition above 70°C [5], [30].…”

Section: Introductionmentioning

confidence: 99%

Interaction of the C-Terminal Peptide of Pulmonary Surfactant Protein B (SP-B) with a Bicellar Lipid Mixture Containing Anionic Lipid

et al. 2013

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The hydrophobic lung surfactant SP-B is essential for respiration. SP-B promotes spreading and adsorption of surfactant at the alveolar air-water interface and may facilitate connections between the surface layer and underlying lamellar reservoirs of surfactant material. SP-B63–78 is a cationic and amphipathic helical peptide containing the C-terminal helix of SP-B. 2H NMR has been used to examine the effect of SP-B63–78 on the phase behavior and dynamics of bicellar lipid dispersions containing the longer chain phospholipids DMPC-d 54 and DMPG and the shorter chain lipid DHPC mixed with a 3∶1∶1 molar ratio. Below the gel-to-liquid crystal phase transition temperature of the longer chain components, bicellar mixtures form small, rapidly reorienting disk-like particles with shorter chain lipid components predominantly found around the highly curved particle edges. With increasing temperature, the particles coalesce into larger magnetically-oriented structures and then into more extended lamellar phases. The susceptibility of bicellar particles to coalescence and large scale reorganization makes them an interesting platform in which to study peptide-induced interactions between lipid assemblies. SP-B63–78 is found to lower the temperature at which the orientable phase transforms to the more extended lamellar phase. The peptide also changes the spectrum of motions contributing to quadrupole echo decay in the lamellar phase. The way in which the peptide alters interactions between bilayered micelle structures may provide some insight into some aspects of the role of full-length SP-B in maintaining a functional surfactant layer in lungs.

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“…The possibility of cubic phase formation by phospholipids also has been mentioned (Epand, 1998). Actually, the most abundant PC is a lamellar phase lipid while PE is a H II former (Chavarha et al, 2012). Although further direct studies are required to demonstrate the presence of inverted structures or H II phase, it is a possibility that the "liquid crystals" such as lamellar (L α ), inverse hexagonal (H II ) and inverse cubic (C II ) may be found in alveolar region.…”

Section: Figurementioning

confidence: 99%