title: Staphylococcus aureus alpha-toxin: characterization of protein/lipid interactions, 2D crystallization on lipid monolayers, and 3D structure.
abstract: Staphylococcus aureus alpha-toxin was characterized with respect to surface activity and its interaction with lipid monolayers. The protein alone had a detergent-like behavior at the air/water interface. Its affinity was higher for negatively charged than for neutral phospholipids. The interaction was pH dependent, showing a maximum increase at pH 7.0. Only a small part of the protein oligomer appeared to be inserted into the monolayers. Crystalline sheets of alpha-toxin were formed using negatively charged phospholipids. Electron microscopy of such areas, at different tilt angles, allowed reconstruction of a three-dimensional model following image processing. The sheets analyzed consisted of two protein layers arranged on a tetragonal lattice. Under the conditions used to grow the crystals the toxin formed 90-A-wide cylinders with a height of 70 A. One of the imposed fourfold axes running perpendicular to the plane of the crystalline layer is positioned at a protein-deficient region which forms a 25-A-wide pore through the oligomer.
authors.affiliation: Centre for Structural Biochemistry, Karolinska Institutet, Huddinge, Sweden. Matthew@csb.ki.se
authors.forename: M J
authors.initials: MJ
authors.lastname: Ellis
authors.forename: H
authors.initials: H
authors.lastname: Hebert
authors.forename: M
authors.initials: M
authors.lastname: Thelestam
mesh_terms: D000388:Air; D001427:Bacterial Toxins / Q000737:chemistry* / Q000633:toxicity; D003460:Crystallization; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000633:toxicity; D006801:Humans; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D008055:Lipids / Q000737:chemistry; D008854:Microscopy, Electron; D015394:Molecular Structure; D013211:Staphylococcus aureus / Q000737:chemistry*; D013499:Surface Properties; D014867:Water
chemical_list: D001427:Bacterial Toxins; D006460:Hemolysin Proteins; D008055:Lipids; C021091:staphylococcal alpha-toxin; D014867:Water