title: Secondary structure and orientation of the pore-forming toxin lysenin in a sphingomyelin-containing membrane.
abstract: Lysenin is a sphingomyelin-recognizing toxin which forms stable oligomers upon membrane binding and causes cell lysis. To get insight into the mechanism of the transition of lysenin from a soluble to a membrane-bound form, surface activity of the protein and its binding to lipid membranes were studied using tensiometric measurements, Fourier-transform infrared spectroscopy (FTIR) and FTIR-linear dichroism. The results showed cooperative adsorption of recombinant lysenin-His at the argon-water interface from the water subphase which suggested self-association of lysenin-His in solution. An assembly of premature oligomers by lysenin-His in solution was confirmed by blue native gel electrophoresis. When a monolayer composed of sphingomyelin and cholesterol was present at the interface, the rate of insertion of lysenin-His into the monolayer was considerably enhanced. Analysis of FTIR spectra of soluble lysenin-His demonstrated that the protein contained 27% beta-sheet, 28% aggregated beta-strands, 10% alpha-helix, 23% turns and loops and 12% different kinds of aggregated forms. In membrane-bound lysenin-His the total content of alpha-helices, turns and loops, and beta-structures did not change, however, the 1636cm(-1) beta-sheet band increased from 18% to 31% at the expense of the 1680cm(-1) beta-sheet structure. Spectral analysis of the amide I band showed that the alpha-helical component was oriented with at 41 degrees to the normal to the membrane, indicating that this protein segment could be anchored in the hydrophobic core of the membrane.
authors.affiliation: Department of Cell Biology, Nencki Institute of Experimental Biology, 02-093 Warsaw, Poland.
authors.forename: Monika
authors.initials: M
authors.lastname: Hereć
authors.forename: Mariusz
authors.initials: M
authors.lastname: Gagoś
authors.forename: Magdalena
authors.initials: M
authors.lastname: Kulma
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Kwiatkowska
authors.forename: Andrzej
authors.initials: A
authors.lastname: Sobota
authors.forename: Wiesław I
authors.initials: WI
authors.lastname: Gruszecki
mesh_terms: D000327:Adsorption; D000388:Air; D006639:Histidine; D008051:Lipid Bilayers / Q000737:chemistry*; D052899:Pore Forming Cytotoxic Proteins / Q000737:chemistry*; D011312:Pressure; D017433:Protein Structure, Secondary; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013109:Sphingomyelins / Q000737:chemistry*; D013997:Time Factors; D014118:Toxins, Biological / Q000737:chemistry*; D014867:Water
chemical_list: D008051:Lipid Bilayers; D052899:Pore Forming Cytotoxic Proteins; D013109:Sphingomyelins; D014118:Toxins, Biological; C107040:lysenin; D014867:Water; D006639:Histidine