title: Secondary structure of the entomocidal toxin from Bacillus thuringiensis subsp. kurstaki HD-73.
abstract: 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 circular dichroism spectra, as well as predictive methods, indicated that the toxin contains 32-40% beta-sheet structure, whereas infrared spectroscopy gave a slightly lower estimate. Thus, all of these approaches are in agreement that the native conformation of Btk HD-73 toxin is highly folded and contains considerable amounts of both alpha-helical and beta-sheet structures. No significant differences were detected in the secondary structure of the toxin either in solution or as a hydrated pellet.
authors.affiliation: Department of Chemistry, University of Ottawa, Ontario, Canada.
authors.forename: C T
authors.initials: CT
authors.lastname: Choma
authors.forename: W K
authors.initials: WK
authors.lastname: Surewicz
authors.forename: P R
authors.initials: PR
authors.lastname: Carey
authors.forename: M
authors.initials: M
authors.lastname: Pozsgay
authors.forename: H
authors.initials: H
authors.lastname: Kaplan
mesh_terms: D001413:Bacillus thuringiensis; D001427:Bacterial Toxins; D002942:Circular Dichroism; D011487:Protein Conformation; D011498:Protein Precursors; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman
chemical_list: C029103:Bacillus thuringiensis protoxin; D001427:Bacterial Toxins; D011498:Protein Precursors