title: Single channel evidence for innate pore-formation by Vibrio parahaemolyticus thermostable direct haemolysin (TDH) in phospholipid bilayers.
abstract: Vibrio parahaemolyticus thermostable direct haemolysin (TDH) is widely considered to be a pore-forming toxin. The protein has no significant homology to other known pore-forming toxins and its mechanism of action in vivo remains undefined. We demonstrate single channel pore-forming activity of V. parahaemolyticus TDH in planar lipid bilayers. Channel conductance ranged between 30-450 pS in 0.5 M KCl with a calculated cation selectivity (P(K)/P(Cl)) of 2.7. Channels were formed in NaCl and choline-Cl with and without cholesterol present and in the presence of neutral or negatively charged phospholipids. Zinc ions did not block pore formation. Whilst various techniques have previously suggested that TDH is a pore-forming toxin, the data in this study provide direct single channel evidence and indicate several features of pore formation in synthetic phospholipid membranes.
authors.affiliation: School of Pharmacy and Biomolecular Sciences, University of Brighton, Lewes Road, Brighton, Sussex BN2 4GJ, UK. s.hardy@bton.ac.uk
authors.forename: Simon P
authors.initials: SP
authors.lastname: Hardy
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nakano
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Iida
mesh_terms: D000595:Amino Acid Sequence; D000838:Anions / Q000378:metabolism; D001427:Bacterial Toxins; D002412:Cations / Q000378:metabolism; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000502:physiology*; D008051:Lipid Bilayers / Q000737:chemistry; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D010743:Phospholipids / Q000737:chemistry; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D014736:Vibrio parahaemolyticus / Q000502:physiology*
chemical_list: D000838:Anions; D001427:Bacterial Toxins; D002412:Cations; D006460:Hemolysin Proteins; D008051:Lipid Bilayers; D010743:Phospholipids; C068489:thermostable direct hemolysin