title: Cryo-EM structure of lysenin pore elucidates membrane insertion by an aerolysin family protein.
abstract: Lysenin from the coelomic fluid of the earthworm Eisenia fetida belongs to the aerolysin family of small β-pore-forming toxins (β-PFTs), some members of which are pathogenic to humans and animals. Despite efforts, a high-resolution structure of a channel for this family of proteins has been elusive and therefore the mechanism of activation and membrane insertion remains unclear. Here we determine the pore structure of lysenin by single particle cryo-EM, to 3.1 Å resolution. The nonameric assembly reveals a long β-barrel channel spanning the length of the complex that, unexpectedly, includes the two pre-insertion strands flanking the hypothetical membrane-insertion loop. Examination of other members of the aerolysin family reveals high structural preservation in this region, indicating that the membrane-insertion pathway in this family is conserved. For some toxins, proteolytic activation and pro-peptide removal will facilitate unfolding of the pre-insertion strands, allowing them to form the β-barrel of the channel.
authors.affiliation: Biosciences, College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK.
authors.forename: Monika
authors.initials: M
authors.lastname: Bokori-Brown
authors.affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Martin
authors.affiliation: Department of Biological Sciences, Birkbeck College, Malet Street, London WC1E 7HX, UK.
authors.forename: Claire E
authors.initials: CE
authors.lastname: Naylor
authors.affiliation: Department of Biological Sciences, Birkbeck College, Malet Street, London WC1E 7HX, UK.
authors.forename: Ajit K
authors.initials: AK
authors.lastname: Basak
authors.affiliation: Biosciences, College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Titball
authors.affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.
authors.forename: Christos G
authors.initials: CG
authors.lastname: Savva
mesh_terms: D001427:Bacterial Toxins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D020285:Cryoelectron Microscopy; D006801:Humans; D008055:Lipids / Q000737:chemistry; D008958:Models, Molecular; D052899:Pore Forming Cytotoxic Proteins / Q000378:metabolism*; D017433:Protein Structure, Secondary; D012995:Solubility; D014118:Toxins, Biological / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D001427:Bacterial Toxins; D008055:Lipids; D052899:Pore Forming Cytotoxic Proteins; D014118:Toxins, Biological; C107040:lysenin; D014867:Water; C032676:aerolysin