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dc.contributor.authorTheeraporn Puntheeranuraken_US
dc.contributor.authorPanapat Uawithyaen_US
dc.contributor.authorLéna Potvinen_US
dc.contributor.authorChanan Angsuthanasombaten_US
dc.contributor.authorJean Louis Schwartzen_US
dc.contributor.otherMahidol Universityen_US
dc.contributor.otherNational Research Council Canadaen_US
dc.contributor.otherUniversite de Montrealen_US
dc.identifier.citationMolecular Membrane Biology. Vol.21, No.1 (2004), 67-74en_US
dc.description.abstractTrypsin activation of Cry4B, a 130-kDa Bacillus thuringiensis (Bt) protein, produces a 65-kDa toxin active against mosquito larvae. The active toxin is made of two protease-resistant products of ca. 45 kDa and ca. 20 kDa. The cloned 21-kDa fragment consisting of the N-terminal region of the toxin was previously shown to be capable of permeabilizing liposomes. The present study was designed to test the following hypotheses: (1) Cry4B, like several other Bt toxins, is a channel-forming toxin in planar lipid bilayers; and (2) the 21-kDa N-terminal region, which maps for the first five helices (α1-α5) of domain 1 in other Cry toxins, and which putatively shares a similar tri-dimensional structure, is sufficient to account for the ion channel activity of the whole toxin. Using circular dichroism spectroscopy and planar lipid bilayers, we showed that the 21-kDa polypeptide existed as an α-helical structure and that both Cry4B and its α1-α5 fragment formed ion channels of 248±44 pS and 207±23 pS, respectively. The channels were cation-selective with a potassium-to-chloride permeability ratio of 6.7 for Cry4B and 4.5 for its fragment. However, contrary to the full-length toxin, the α1-α5 region formed channels at low dose; they tended to remain locked in their open state and displayed flickering activity bouts. Thus, like the full-length toxin, the α1-α5 region is a functional channel former. A pH-dependent, yet undefined region of the toxin may be involved in regulating the channel properties.en_US
dc.rightsMahidol Universityen_US
dc.subjectBiochemistry, Genetics and Molecular Biologyen_US
dc.titleIon channels formed in planar lipid bilayers by the dipteran-specific Cry4B Bacillus thuringiensis toxin and its α1-α5 fragmenten_US
Appears in Collections:Scopus 2001-2005

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