title: Dimeric N-terminal segment of human surfactant protein B (dSP-B(1-25)) has enhanced surface properties compared to monomeric SP-B(1-25).
abstract: Surfactant protein B (SP-B) is a 17-kDa dimeric protein produced by alveolar type II cells. Its main function is to lower the surface tension by inserting lipids into the air/liquid interface of the lung. SP-B's function can be mimicked by a 25-amino acid peptide, SP-B(1-25), which is based on the N-terminal sequence of SP-B. We synthesized a dimeric version of this peptide, dSP-B(1-25), and the two peptides were tested for their surface activity. Both SP-B(1-25) and dSP-B(1-25) showed good lipid mixing and adsorption activities. The dimeric peptide showed activity comparable to that of native SP-B in the pressure-driven captive bubble surfactometer. Spread surface films led to stable near-zero minimum surface tensions during cycling while protein free, and films containing SP-B(1-25) lost material from the interface during compression. We propose that dimerization of the peptide is required to create a lipid reservoir attached to the monolayer from which new material can enter the surface film upon expansion of the air/liquid interface. The dimeric state of SP-B can fulfill the same function in vivo.
authors.affiliation: Department of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, Utrecht University, 3508 TD Utrecht, the Netherlands.
authors.forename: E J
authors.initials: EJ
authors.lastname: Veldhuizen
authors.forename: A J
authors.initials: AJ
authors.lastname: Waring
authors.forename: F J
authors.initials: FJ
authors.lastname: Walther
authors.forename: J J
authors.initials: JJ
authors.lastname: Batenburg
authors.forename: L M
authors.initials: LM
authors.lastname: van Golde
authors.forename: H P
authors.initials: HP
authors.lastname: Haagsman
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D000595:Amino Acid Sequence; D002118:Calcium / Q000737:chemistry; D019281:Dimerization; D005453:Fluorescence; D006801:Humans; D008055:Lipids / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry; D008567:Membranes, Artificial; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry; D010715:Phosphatidylglycerols / Q000737:chemistry; D011510:Proteolipids / Q000737:chemistry*; D011663:Pulmonary Surfactants / Q000737:chemistry*; D012995:Solubility; D013499:Surface Properties; D013500:Surface Tension
chemical_list: D008055:Lipids; D008081:Liposomes; D008567:Membranes, Artificial; D010446:Peptide Fragments; D010713:Phosphatidylcholines; D010715:Phosphatidylglycerols; D011510:Proteolipids; D011663:Pulmonary Surfactants; D015060:1,2-Dipalmitoylphosphatidylcholine; C021248:1-palmitoyl-2-pyrenedecanoylphosphatidylcholine; C060037:1-palmitoyl-2-oleoylglycero-3-phosphoglycerol; D002118:Calcium