title: Alpha-cobratoxin: proton NMR assignments and solution structure.
abstract: The solution structure of alpha-cobratoxin, a neurotoxin purified from the venom of the snake Naja naja siamensis, at pH 3.2 is reported. Sequence-specific assignments of the NMR resonances was attained by a combination of a generalized main-chain-directed strategy and of the sequential method. The NMR data show the presence of a triple-stranded beta-sheet (residues 19-25, 36-41, and 52-57), a short helix, and turns. An extensive number of NOE cross peaks were identified in the NOESY NMR maps. These were applied as distance constraints in a molecular modeling protocol which includes distance geometry and dynamical simulated annealing calculations. A single family of structures is observed which fold in such a way that three major loops emerge from a globular head. The solution and crystal structures of alpha-cobratoxin are very similar. This is in clear contrast to results reported for alpha-bungarotoxin where significant differences exist.
authors.affiliation: Institut de Chimie des Substances Naturelles, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
authors.forename: R
authors.initials: R
authors.lastname: Le Goas
authors.forename: S R
authors.initials: SR
authors.lastname: LaPlante
authors.forename: A
authors.initials: A
authors.lastname: Mikou
authors.forename: M A
authors.initials: MA
authors.lastname: Delsuc
authors.forename: E
authors.initials: E
authors.lastname: Guittet
authors.forename: M
authors.initials: M
authors.lastname: Robin
authors.forename: I
authors.initials: I
authors.lastname: Charpentier
authors.forename: J Y
authors.initials: JY
authors.lastname: Lallemand
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003039:Cobra Neurotoxin Proteins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011522:Protons; D012996:Solutions; D013329:Structure-Activity Relationship
chemical_list: D003039:Cobra Neurotoxin Proteins; D011522:Protons; D012996:Solutions; C025154:alpha-cobratoxin