title: Canavalia ensiformis urease, Jaburetox and derived peptides form ion channels in planar lipid bilayers.
abstract: Ureases catalyze the hydrolysis of urea into NH3 and CO2. They are synthesized by plants, fungi and bacteria but not by animals. Ureases display biological activities unrelated to their enzymatic activity, i.e., platelet and neutrophil activation, fungus inhibition and insecticidal effect. Urease from Canavalia ensiformis (jack bean) is toxic to several hemipteran and coleopteran insects. Jaburetox is an insecticidal fragment derived from jack bean urease. Among other effects, Jaburetox has been shown to interact with lipid vesicles. In this work, the ion channel activity of C. ensiformis urease, Jaburetox and three deletion mutants of Jaburetox (one lacking the N-terminal region, one lacking the C-terminal region and one missing the central β-hairpin) were tested on planar lipid bilayers. All proteins formed well resolved, highly cation-selective channels exhibiting two conducting states whose conductance ranges were 7-18pS and 32-79pS, respectively. Urease and the N-terminal mutant of Jaburetox were more active at negative potentials, while the channels of the other peptides did not display voltage-dependence. This is the first direct demonstration of the capacity of C. ensiformis urease and Jaburetox to permeabilize membranes through an ion channel-based mechanism, which may be a crucial step of their diverse biological activities, including host defense.
authors.affiliation: Graduate Program in Cellular and Molecular Biology, Center of Biotechnology, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS CEP 91501-970, Brazil.
authors.forename: Angela R
authors.initials: AR
authors.lastname: Piovesan
authors.affiliation: Graduate Program in Cellular and Molecular Biology, Center of Biotechnology, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS CEP 91501-970, Brazil; Department of Biophysics, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS CEP 91501-970, Brazil.
authors.forename: Anne H S
authors.initials: AH
authors.lastname: Martinelli
authors.affiliation: Graduate Program in Cellular and Molecular Biology, Center of Biotechnology, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS CEP 91501-970, Brazil.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Ligabue-Braun
authors.affiliation: Groupe d'étude des protéines membranaires (GÉPROM, FQR-S) and Department of Physiology, Faculty of Medicine, Université de Montréal, Montreal, Quebec H3C 3J7, Canada; Centre SÈVE (FQR-NT), Université de Sherbrooke, Sherbrooke, Quebec J1K 2R, Canada. Electronic address: jean-louis.schwartz@umontreal.ca.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Schwartz
authors.affiliation: Graduate Program in Cellular and Molecular Biology, Center of Biotechnology, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS CEP 91501-970, Brazil; Department of Biophysics, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS CEP 91501-970, Brazil. Electronic address: ccarlini@ufrgs.br.
authors.forename: Celia R
authors.initials: CR
authors.lastname: Carlini
mesh_terms: D000595:Amino Acid Sequence; D032449:Canavalia / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002463:Cell Membrane Permeability; D007306:Insecticides / Q000737:chemistry / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism*; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D014510:Urease / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D007306:Insecticides; D007473:Ion Channels; D008051:Lipid Bilayers; D010455:Peptides; D010940:Plant Proteins; D014510:Urease
keywords: Canavalia ensiformis urease; Insecticidal protein; Ion channel; Membrane permeabilization; Planar lipid bilayer; Pore-forming toxin