title: Infrared spectroscopy study on the conformational changes leading to pore formation of the toxin sticholysin II.
abstract: The structure of the actinoporin sticholysin II (StnII) in the pore state was investigated by Fourier transform infrared spectroscopy in the attenuated total reflection configuration. 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/cholesterol unilamellar vesicles were employed. The alpha-helix content increases in approximately 30% upon lipid binding, which agrees with an extension of eight or nine residues at the N-terminal helix. Furthermore, analyses of dichroic spectra show that the extended N-terminal helix would have a 31 degrees tilt with respect to the membrane normal. The orientation of the central beta-sandwich was also estimated. In addition, it was detected that StnII alters the orientation of the lipid acyl chains. (1)H/(2)H exchange experiments sustain a mainly superficial interaction between StnII and the membrane, with no protection of the beta-sandwich. The implications of the results in the mechanism of pore formation are discussed.
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid, Spain. alegre@bbm1.ucm.es
authors.forename: Jorge
authors.initials: J
authors.lastname: Alegre-Cebollada
authors.forename: Alvaro
authors.initials: A
authors.lastname: Martínez del Pozo
authors.forename: José G
authors.initials: JG
authors.lastname: Gavilanes
authors.forename: Erik
authors.initials: E
authors.lastname: Goormaghtigh
mesh_terms: D000818:Animals; D002784:Cholesterol / Q000378:metabolism; D003064:Cnidarian Venoms / Q000737:chemistry* / Q000378:metabolism; D008567:Membranes, Artificial; D010713:Phosphatidylcholines / Q000378:metabolism; D052899:Pore Forming Cytotoxic Proteins / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012615:Sea Anemones; D013055:Spectrophotometry, Infrared; D014118:Toxins, Biological / Q000737:chemistry* / Q000378:metabolism
chemical_list: D003064:Cnidarian Venoms; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D052899:Pore Forming Cytotoxic Proteins; D014118:Toxins, Biological; C404794:sticholysin II; D002784:Cholesterol; C028694:1-palmitoyl-2-oleoylphosphatidylcholine