The mechanism of membrane insertion for a cholesterol-dependent cytolysin: a novel paradigm for pore-forming toxins.
Perfringolysin O (PFO), a water-soluble monomeric cytolysin secreted by pathogenic Clostridium perfringens, oligomerizes and forms large pores upon encountering cholesterol-containing membranes. Whereas all pore-forming bacterial toxins examined previously have been shown to penetrate the membrane using a single amphipathic beta hairpin per polypeptide, cysteine-scanning mutagenesis and multiple independent fluorescence techniques here reveal that each PFO monomer contains a second domain involved in pore formation, and that each of the two amphipathic beta hairpins completely spans the membrane. In the soluble monomer, these transmembrane segments are folded into six alpha helices. The insertion of two transmembrane hairpins per toxin monomer and the major change in secondary structure are striking and define a novel paradigm for the mechanism of membrane insertion by a cytolytic toxin.
Shatursky
O
O
Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City 73190, USA.
Heuck
A P
AP
Shepard
L A
LA
Rossjohn
J
J
Parker
M W
MW
Johnson
A E
AE
Tweten
R K
RK
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001427:Bacterial Toxins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D003016:Clostridium perfringens / Q000502:physiology*; D003545:Cysteine; D005456:Fluorescent Dyes; D006460:Hemolysin Proteins / Q000378:metabolism; D008081:Liposomes; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010713:Phosphatidylcholines; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013113:Spin Labels
D001427:Bacterial Toxins; D005456:Fluorescent Dyes; D006460:Hemolysin Proteins; D008081:Liposomes; D010713:Phosphatidylcholines; D011994:Recombinant Proteins; D013113:Spin Labels; C020452:Clostridium perfringens theta-toxin; D003545:Cysteine; C028694:1-palmitoyl-2-oleoylphosphatidylcholine