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Physical properties and surface activity of surfactant‐like membranes containing the cationic and hydrophobic peptide KL 4
Author(s) -
Sáenz Alejandra,
Cañadas Olga,
Bagatolli Luís A.,
Johnson Mark E.,
Casals Cristina
Publication year - 2006
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2006.05258.x
Subject(s) - popc , chemistry , vesicle , membrane , pulmonary surfactant , adsorption , phosphatidylcholine , peptide , lipid bilayer , phosphatidylglycerol , chromatography , crystallography , organic chemistry , phospholipid , biochemistry
Surfactant‐like membranes containing the 21‐residue peptide KLLLLKLLLLKLLLLKLLLLK (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 α‐helical secondary structure in POPG‐ or POPC‐containing membranes, and a β‐sheet structure in DPPC/PA vesicles. As the concentration of the peptide increased, KL 4 interconverted to a β‐sheet structure in DPPC/POPG/PA or DPPC/POPC/PA vesicles. Ca 2+ favored α⇆β 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 air–water interface.