Ion Channels Induced in Planar Lipid Bilayers by the Bacillus thuringiensis Toxin Cry1Aa in the Presence of Gypsy Moth (Lymantria dispar) Brush Border Membrane

Ion Channels Induced in Planar Lipid Bilayers by the Bacillus thuringiensis Toxin Cry1Aa in the... The apical brush border membrane, the main target site of Bacillus thuringiensis toxins, was isolated from gypsy moth (Lymantria dispar) larval midguts and fused to artificial planar lipid bilayer membranes. Under asymmetrical N-methyl-d-glucamine-HCl conditions (450 mm cis/150 mm trans, pH 9.0), which significantly reduce endogenous channel activity, trypsin-activated Cry1Aa, a B. thuringiensis insecticidal protein active against the gypsy moth in vivo, induced a large increase in bilayer membrane conductance at much lower concentrations (1.1–2.15 nm) than in receptor-free bilayer membranes. At least 5 main single-channel transitions with conductances ranging from 85 to 420 pS were resolved. These Cry1Aa channels share similar ionic selectivity with P Cl/P NMDG permeability ratios ranging from 4 to 8. They show no evidence of current rectification. Analysis of the macroscopic current flowing through the composite bilayer suggested voltage-dependence of several channels. In comparison, the conductance of the pores formed by 100–500 nm Cry1Aa in receptor-free bilayer membranes was significantly smaller (about 8-fold) and their P Cl/P NMDG permeability ratios were also reduced (2- to 4-fold). This study provides a detailed demonstration that the target insect midgut brush border membrane material promotes considerably pore formation by a B. thuringiensis Cry toxin and that this interaction results in altered channel properties. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Ion Channels Induced in Planar Lipid Bilayers by the Bacillus thuringiensis Toxin Cry1Aa in the Presence of Gypsy Moth (Lymantria dispar) Brush Border Membrane

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 2001 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232-001-0071-8
Publisher site
See Article on Publisher Site

Abstract

The apical brush border membrane, the main target site of Bacillus thuringiensis toxins, was isolated from gypsy moth (Lymantria dispar) larval midguts and fused to artificial planar lipid bilayer membranes. Under asymmetrical N-methyl-d-glucamine-HCl conditions (450 mm cis/150 mm trans, pH 9.0), which significantly reduce endogenous channel activity, trypsin-activated Cry1Aa, a B. thuringiensis insecticidal protein active against the gypsy moth in vivo, induced a large increase in bilayer membrane conductance at much lower concentrations (1.1–2.15 nm) than in receptor-free bilayer membranes. At least 5 main single-channel transitions with conductances ranging from 85 to 420 pS were resolved. These Cry1Aa channels share similar ionic selectivity with P Cl/P NMDG permeability ratios ranging from 4 to 8. They show no evidence of current rectification. Analysis of the macroscopic current flowing through the composite bilayer suggested voltage-dependence of several channels. In comparison, the conductance of the pores formed by 100–500 nm Cry1Aa in receptor-free bilayer membranes was significantly smaller (about 8-fold) and their P Cl/P NMDG permeability ratios were also reduced (2- to 4-fold). This study provides a detailed demonstration that the target insect midgut brush border membrane material promotes considerably pore formation by a B. thuringiensis Cry toxin and that this interaction results in altered channel properties.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Nov 1, 2001

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