Solution structure of gamma 1-H and gamma 1-P thionins from barley and wheat endosperm determined by 1H-NMR: a structural motif common to toxic arthropod proteins.
The complete assignment of the proton NMR spectra of the homologous gamma 1-hordothionin and gamma 1-purothionin (47 amino acids, 4 disulfide bridges) from barley and wheat, respectively, has been performed by two-dimensional sequence-specific methods. A total of 299 proton-proton distance constraints for gamma 1-H and 285 for gamma 1-P derived from NOESY spectra have been used to calculate the three-dimensional solution structures. Initial structures have been generated by distance geometry methods and further refined by dynamical simulated annealing calculations. Both proteins show identical secondary and tertiary structure with a well-defined triple-stranded antiparallel beta-sheet (residues 1-6, 31-34, and 39-47), an alpha-helix (residues 16-28), and the corresponding connecting loops. Three disulfide bridges are located in the hydrophobic core holding together the alpha-helix and the beta-sheet and forming a cysteine-stabilized alpha-helical (CSH) motif. Moreover, a clustering of positive charges is observed on the face of the beta-sheet opposite to the helix. The three-dimensional structures of the gamma-thionins differ remarkably from plant alpha- and beta-thionins and crambin. However, they show a higher structural analogy with scorpion toxins and insect defensins which also present the CSH motif.
Bruix
M
M
Instituto de Estructura de la Materia, CSIC, Madrid, Spain.
Jiménez
M A
MA
Santoro
J
J
González
C
C
Colilla
F J
FJ
Méndez
E
E
Rico
M
M
D000595:Amino Acid Sequence; D023181:Antimicrobial Cationic Peptides; D001180:Arthropod Venoms / Q000737:chemistry*; D001467:Hordeum / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry*; D011487:Protein Conformation; D011522:Protons; D017386:Sequence Homology, Amino Acid; D014908:Triticum / Q000737:chemistry*
D023181:Antimicrobial Cationic Peptides; D001180:Arthropod Venoms; D010940:Plant Proteins; D011522:Protons; C036092:hordothionin protein, Hordeum vulgare; C016085:purothionin