title: VCA1008: An Anion-Selective Porin of Vibrio Cholerae.
abstract: A putative porin function has been assigned to VCA1008 of Vibrio cholerae. Its coding gene, vca1008, is expressed upon colonization of the small intestine in infant mice and human volunteers, and is essential for infection. In vitro, vca1008 is expressed under inorganic phosphate limitation and, in this condition, VCA1008 is the major outer membrane protein of the bacterium. Here, we provide the first functional characterization of VCA1008 reconstituted into planar lipid bilayers. Our main findings were: 1) VCA1008 forms an ion channel that, at high voltage (~±100 mV), presents a voltage-dependent activity and displays closures typical of trimeric porins, with a conductance of 4.28±0.04 nS (n=164) in 1M KCl; 2) It has a preferred selectivity for anions over cations; 3) Its conductance saturates with increasing inorganic phosphate concentration, suggesting VCA1008 contains binding site(s) for this anion; 4) Its ion selectivity is controlled by both fixed charged residues within the channel and diffusion along the pore; 5) Partitioning of poly (ethylene glycol)s (PEGs) of different molecular mass suggests that VCA1008 channel has a pore exclusion limit of 0.9 nm.
authors.affiliation: Structure et Fonction des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Faculté des Sciences, Université Libre de Bruxelles, Campus Plaine (CP 206/2), B - 1050 Brussels, Belgium.
authors.forename: Carolina L
authors.initials: CL
authors.lastname: Goulart
authors.affiliation: Laboratório de Física Biológica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Paulo M
authors.initials: PM
authors.lastname: Bisch
authors.affiliation: Laboratório de Física Biológica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Wanda M A
authors.initials: WM
authors.lastname: von Krüger
authors.affiliation: Structure et Fonction des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Faculté des Sciences, Université Libre de Bruxelles, Campus Plaine (CP 206/2), B - 1050 Brussels, Belgium. Electronic address: fhomble@ulb.ac.be.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Homblé
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D001692:Biological Transport; D004058:Diffusion; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D015640:Ion Channel Gating; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D051379:Mice; D010710:Phosphates / Q000737:chemistry* / Q000378:metabolism; D011092:Polyethylene Glycols / Q000737:chemistry / Q000378:metabolism; D018272:Porins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D055503:Protein Multimerization; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055672:Static Electricity; D014734:Vibrio cholerae / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D008051:Lipid Bilayers; D010710:Phosphates; D018272:Porins; D011994:Recombinant Proteins; D011092:Polyethylene Glycols
keywords: Donnan potential; ion channel selectivity; porin