Marianne Pozsgay's research while affiliated with University of Ottawa and other places
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Publications (7)
Trypsin is shown to generate an insecticidal toxin from the 130-kDa protoxin of Bacillus thuringiensis subsp. kurstaki HD-73 by an unusual proteolytic process. Seven specific cleavages are shown to occur in an ordered sequence starting at the C-terminus of the protoxin and proceeding toward the N-terminal region. At each step, C-terminal fragments...
Bacillus thuringiensis produces a 130-140 kDa insecticidal protein in the form of a bipyramidal crystal. The protein in the crystals from the subspecies kurstaki HD-1 and entomocidus was found to contain 16-18 cysteine residues per molecule, present primarily in the disulphide form as cystine. Evidence that all the cysteine residues form symmetrica...
The secondary structure of the toxin from Bacillus thuringiensis subsp. kurstaki (Btk) HD-73 was estimated by Raman, infrared, and circular dichroism spectroscopy, and by predictive methods. Circular dichroism and infrared spectroscopy gave an estimate of 33-40% alpha-helix, whereas Raman and predictive methods gave approximately 20%. Raman and cir...
A procedure for the selective isolation of the C-terminal peptides from enzymatic digests of proteins is described. The methodology is based on the diagonal electrophoretic procedure described by R. G. Duggleby and H. Kaplan (1975) Anal. Biochem. 65, 346-354). The carboxyl groups in the protein are amidated with [14C]-methylamine followed by enzyma...
We report a simple three-step method of generating a homogeneous toxic fragment (toxin) in high yield from B. thuringiensis var. kurstaki. Purified crystals were digested with trypsin at pH 10.5, followed by (NH4)2SO4 precipitation and dialysis. For the HD73 strain the preparation is toxic to eastern-spruce-budworm (Choristoneura fuminiferana) larv...
The Raman spectrum of the endotoxin crystals from Bacillus thuringiensis var. kurstaki NRD12 is found to resemble closely that for crystals of the strain kurstaki HD1 (P. R. Carey et al., 1986). Since the Raman data provide detailed molecular information on the crystal proteins, the protoxins of HD1 and NRD12 must be in similar conformations in the...
A novel method, using a modified Pasteur pipette and a clinical centrifuge, has been developed for preparing highly purified δ-endotoxin crystals from Bacillus thuringiensis. Analysis of the Raman spectra of the crystals from B. thuringiensis subspecies kurstaki HD1 and HD73 provides detailed structural information on the protoxin protein component...
Citations
... Because, the exogenous chromophore may be non-covalently bound to the ICPs of Bt toxic protein. The chromophore absorbs light and transfers part of its energy to the neighboring O 2 molecule, producing singlet oxygen (Carey et al., 1986). Singlet oxygen is highly reactive, and causes widespread chemical damage to proteins (Grossweiner, 1976), leading to the inactivation of Bt toxic proteins. ...
... In addition, a main disadvantage of biopesticides is their loss of activity upon the deleterious action of abiotic factors in the field including the sunlight. The decrease in stability with loss of effectiveness of B. thuringiensis-based biopesticides after exposure to the UV radiation from sunlight has been already reported (Jalali et al., 2020;Pozsgay et al., 1987;Sansinenea et al., 2015). ...
... Most Cry family proteins are considered to be composed of two distinct structural fragments, N-terminal and C-terminal. N-terminal is highly conserved and functions in toxicity, and C-terminal mainly acts to maintain the correct conformation of proteins [17] . Some evidence has supported that only overexpressing N-terminal fragments could provide e cient insect-resistance in transgenic crops, such as MON810 (Monsanto) [8] . ...
... Then the activated toxins bind with the specific cell surface glycoprotein receptors on causing ionic imbalance on the gut lining cells,that initiate the destruction pathway of the cells. These result in the death of the insect (Choma et al., 1990). ...
Reference: GM crops: Their benefits and drawbacks
... The bipyramidal crystals, formed by Cry1A protoxins of 120–140 kDa, have been extensively studied during past decades . These bodies are soluble into high pH and produce $70 kDa toxins upon trypsinization [6,7]. The 3-D structure of the Cry1Aa toxin showed a conserved three-domain configuration (domains I, II and III), which seems to be essential for the lytic activity [8]. ...
... However, when this particular protein comes into contact with trypsin or the digestive enzymes found in the digestive tract of the intended insect, it will undergo degradation that leads to the elimination of the amino acid located at position 766, resulting in the protein's inactivation. Fortunately, the removal of the amino acid at position 766 and subsequent inactivation of the protein does not have any negative impact on its ability to target the intended host, as well as the remaining active portion of the Nterminal that retains its activity (Bietlot et al., 1989). Transgenics: Vector-Mediated Gene Transfer. ...
... The Cry1A protein is digested into its activated form at amino acid residue 28R of N-terminus and residue 623K of the C-terminus (Nagamatsu et al. 1984;Bietlot et al. 1989). It is well known that Trypsin and chymotrypsin are the primary proteases in the midgut; on the basis of sequence analysis and the location of arginine and lysine residues, the insecticidal activities of 10 different Cry1Ah toxin fragments were investigated: a truncated protein consisting of amino acid residues 50I to 639E exhibited the same toxicity as the full-length Cry1Ah protein. ...
