title: Toxin-induced pore formation is hindered by intermolecular hydrogen bonding in sphingomyelin bilayers.
abstract: Sticholysin I and II (StnI and StnII) are pore-forming toxins that use sphingomyelin (SM) for membrane binding. We examined how hydrogen bonding among membrane SMs affected the StnI- and StnII-induced pore formation process, resulting in bilayer permeabilization. We compared toxin-induced permeabilization in bilayers containing either SM or dihydro-SM (lacking the trans Δ(4) double bond of the long-chain base), since their hydrogen-bonding properties are known to differ greatly. We observed that whereas both StnI and StnII formed pores in unilamellar vesicles containing palmitoyl-SM or oleoyl-SM, the toxins failed to similarly form pores in vesicles prepared from dihydro-PSM or dihydro-OSM. In supported bilayers containing OSM, StnII bound efficiently, as determined by surface plasmon resonance. However, StnII binding to supported bilayers prepared from dihydro-OSM was very low under similar experimental conditions. The association of the positively charged StnII (at pH7.0) with unilamellar vesicles prepared from OSM led to a concentration-dependent increase in vesicle charge, as determined from zeta-potential measurements. With dihydro-OSM vesicles, a similar response was not observed. Benzyl alcohol, which is a small hydrogen-bonding compound with affinity to lipid bilayer interfaces, strongly facilitated StnII-induced pore formation in dihydro-OSM bilayers, suggesting that hydrogen bonding in the interfacial region originally prevented StnII from membrane binding and pore formation. We conclude that interfacial hydrogen bonding was able to affect the membrane association of StnI- and StnII, and hence their pore forming capacity. Our results suggest that other types of protein interactions in bilayers may also be affected by hydrogen-bonding origination from SMs.
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense, Madrid, Spain; Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
authors.forename: Sara
authors.initials: S
authors.lastname: García-Linares
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense, Madrid, Spain; Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
authors.forename: Juan
authors.initials: J
authors.lastname: Palacios-Ortega
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland; Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Yasuda
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
authors.forename: Mia
authors.initials: M
authors.lastname: Åstrand
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense, Madrid, Spain.
authors.forename: José G
authors.initials: JG
authors.lastname: Gavilanes
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense, Madrid, Spain.
authors.forename: Álvaro
authors.initials: Á
authors.lastname: Martínez-del-Pozo
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland. Electronic address: jpslotte@abo.fi.
authors.forename: J Peter
authors.initials: JP
authors.lastname: Slotte
mesh_terms: D006860:Hydrogen Bonding; D008051:Lipid Bilayers; D018272:Porins / Q000494:pharmacology*; D013109:Sphingomyelins / Q000737:chemistry / Q000378:metabolism*; D020349:Surface Plasmon Resonance
chemical_list: D008051:Lipid Bilayers; D018272:Porins; D013109:Sphingomyelins
keywords: Permeabilization; Sphingomyelinase; Sticholysin; Surface plasmon resonance