title: Structure and function of a unique pore-forming protein from a pathogenic acanthamoeba.
abstract: Human pathogens often produce soluble protein toxins that generate pores inside membranes, resulting in the death of target cells and tissue damage. In pathogenic amoebae, this has been exemplified with amoebapores of the enteric protozoan parasite Entamoeba histolytica. Here we characterize acanthaporin, to our knowledge the first pore-forming toxin to be described from acanthamoebae, which are free-living, bacteria-feeding, unicellular organisms that are opportunistic pathogens of increasing importance and cause severe and often fatal diseases. We isolated acanthaporin from extracts of virulent Acanthamoeba culbertsoni by tracking its pore-forming activity, molecularly cloned the gene of its precursor and recombinantly expressed the mature protein in bacteria. Acanthaporin was cytotoxic for human neuronal cells and exerted antimicrobial activity against a variety of bacterial strains by permeabilizing their membranes. The tertiary structures of acanthaporin's active monomeric form and inactive dimeric form, both solved by NMR spectroscopy, revealed a currently unknown protein fold and a pH-dependent trigger mechanism of activation.
authors.affiliation: Zoological Institute, Zoophysiology, Christian-Albrechts Universität zu Kiel, Kiel, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Michalek
authors.forename: Frank D
authors.initials: FD
authors.lastname: Sönnichsen
authors.forename: Rainer
authors.initials: R
authors.lastname: Wechselberger
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Dingley
authors.forename: Chien-Wen
authors.initials: CW
authors.lastname: Hung
authors.forename: Annika
authors.initials: A
authors.lastname: Kopp
authors.forename: Hans
authors.initials: H
authors.lastname: Wienk
authors.forename: Maren
authors.initials: M
authors.lastname: Simanski
authors.forename: Rosa
authors.initials: R
authors.lastname: Herbst
authors.forename: Inken
authors.initials: I
authors.lastname: Lorenzen
authors.forename: Francine
authors.initials: F
authors.lastname: Marciano-Cabral
authors.forename: Christoph
authors.initials: C
authors.lastname: Gelhaus
authors.forename: Thomas
authors.initials: T
authors.lastname: Gutsmann
authors.forename: Andreas
authors.initials: A
authors.lastname: Tholey
authors.forename: Joachim
authors.initials: J
authors.lastname: Grötzinger
authors.forename: Matthias
authors.initials: M
authors.lastname: Leippe
mesh_terms: D000048:Acanthamoeba / Q000737:chemistry* / Q000472:pathogenicity; D000595:Amino Acid Sequence; D019281:Dimerization; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry* / Q000502:physiology*; D013329:Structure-Activity Relationship; D014774:Virulence
chemical_list: D015800:Protozoan Proteins