Orthorhombic crystals and three-dimensional structure of the potent toxin II from the scorpion Androctonus australis Hector

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 85; no. 20; pp. 7443 - 7447
• Main Authors: Fontecilla-Camps, J.C, Habersetzer-Rochat, C, Rochat, H
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01.10.1988; National Acad Sciences
• Subjects: ACIDE AMINE; Amino Acid Sequence; AMINO ACIDS; AMINOACIDOS; Androctonus australis; Animals; Atoms; Biochemistry; Biochemistry. Physiology. Immunology; Biological and medical sciences; Buthidae; Crystal structure; Crystallization; Crystals; ESCORPION; Fundamental and applied biological sciences. Psychology; Hydrogen bonds; Insecta; Invertebrates; Models, Chemical; Molecular Sequence Data; Molecules; Neurotoxins - analysis; NUCLEOTIDE; NUCLEOTIDES; NUCLEOTIDOS; Physiology. Development; Protein Conformation; PROTEINAS; PROTEINE; PROTEINS; Reptilian Proteins; Salts; SCORPION; Scorpion Venoms - analysis; SCORPIONS; Solvents; STRUCTURAL FORMULAS; toxin II; TOXINAS; TOXINE; TOXINS; Toxin; Arachnida; Scorpionides; Buthidae; Arthropoda; Crystals; Invertebrata; Spatial structure; Structural analysis
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.85.20.7443

Orthorhombic crystals (space group P212121, a = 45.94 angstrom, b = 40.68 angstrom, c = 29.93 angstrom) of the potent scorpion α -toxin II from Androctonus australis Hector were grown using sterile techniques. The structure was solved by a combination of heavy-atom and model phasing. Subsequently, it was refined at 1.8 angstrom resolution by a fast-Fourier restrained least-squares procedure. The crystallographic R factor is 0.152 for data with 7.0 angstrom > d > 1.8 angstrom and F > 2.5σ (F) and 0.177 when all data are considered. Eighty-nine solvent molecules have been incorporated into the model. The dense core formed by the α -helical and antiparallel β -sheet moieties and three of the four disulfide bridges is similar in variant 3, a toxin purified from the North American scorpion Centruroides sculpturatus, and in toxin II. However, the two molecules differ markedly in the orientation of loops protruding from the core. Toxin II seems to contain several highly ordered solvent molecules. Eight of them occupy a cavity consisting of the C-terminal region and a loop found only in scorpion α -toxins. The highly reactive and pharmacologically important Lys-58 is found at one of the extremes of this cavity, where it establishes a series of hydrogen bonds with protein and solvent atoms. The reactivities of the five lysine residues of toxin II are highly correlated with the formation of hydrogen bonds, hydrophobic interactions, and salt links.