title: Refined structure of charybdotoxin: common motifs in scorpion toxins and insect defensins.
abstract: Conflicting three-dimensional structures of charybdotoxin (Chtx), a blocker of K+ channels, have been previously reported. A high-resolution model depicting the tertiary structure of Chtx has been obtained by DIANA and X-PLOR calculations from new proton nuclear magnetic resonance (NMR) data. The protein possesses a small triple-stranded antiparallel beta sheet linked to a short helix by two disulfides and to an extended fragment by one disulfide, respectively. This motif also exists in all known structures of scorpion toxins, irrespective of their size, sequence, and function. Strikingly, antibacterial insect defensins also adopt this folding pattern.
authors.affiliation: Département d'Ingénierie et d'Etudes des Protéines, Gif sur Yvette, France.
authors.forename: F
authors.initials: F
authors.lastname: Bontems
authors.forename: C
authors.initials: C
authors.lastname: Roumestand
authors.forename: B
authors.initials: B
authors.lastname: Gilquin
authors.forename: A
authors.initials: A
authors.lastname: Ménez
authors.forename: F
authors.initials: F
authors.lastname: Toma
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001798:Blood Proteins / Q000648:ultrastructure*; D018999:Charybdotoxin; D023082:Defensins; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009498:Neurotoxins / Q000737:chemistry*; D015221:Potassium Channels / Q000187:drug effects; D011487:Protein Conformation; D012604:Scorpion Venoms / Q000737:chemistry*; D012605:Scorpions; D016415:Sequence Alignment
chemical_list: D001798:Blood Proteins; D023082:Defensins; D009498:Neurotoxins; D015221:Potassium Channels; D012604:Scorpion Venoms; D018999:Charybdotoxin