title: Structural and functional studies of a synthetic peptide mimicking a proposed membrane inserting region of a Bacillus thuringiensis delta-endotoxin.
abstract: In order to study the mechanism of action of Bacillus thuringiensis delta-endotoxins, a synthetic 31-mer peptide corresponding to the sequence of a putative pore-forming segment of the CrylA(c) toxin was characterized structurally and functionally. The peptide maps onto the central helix (alpha 5) of the six-helix bundle of domain I of the crystal structure of the CryIIIA toxin. CD and NMR spectroscopic studies indicated that the peptide exists as an alpha-helix in methanol and a random coil in water. The peptide associated with liposomes at pH 4.7 and formed discrete, characterizable channels in planar lipid bilayers at low pHs. These channels had a conductance value of 60 picosiemens (pS). It is possible that this helix is a component of the transmembrane pore formed by B. thuringiensis delta-endotoxins in vivo.
authors.affiliation: Department of Biochemistry, University of Cambridge, UK.
authors.forename: C E
authors.initials: CE
authors.lastname: Cummings
authors.forename: G
authors.initials: G
authors.lastname: Armstrong
authors.forename: T C
authors.initials: TC
authors.lastname: Hodgman
authors.forename: D J
authors.initials: DJ
authors.lastname: Ellar
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001427:Bacterial Toxins; D002462:Cell Membrane / Q000378:metabolism; D002942:Circular Dichroism; D004731:Endotoxins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006460:Hemolysin Proteins; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry* / Q000235:genetics; D017433:Protein Structure, Secondary
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; D006460:Hemolysin Proteins; D008051:Lipid Bilayers; D010455:Peptides; C030956:insecticidal crystal protein, Bacillus Thuringiensis