R. Bhaskaran et C. Yu, NMR-SPECTRA AND RESTRAINED MOLECULAR-DYNAMICS OF THE MUSHROOM TOXIN VIROISIN, International journal of peptide & protein research, 43(4), 1994, pp. 393-401
The conformation of viroisin, the monocyclic toxic heptapeptide of the
virotoxin family from mushroom Amanita virosa, was analysed using two
-dimensional nuclear magnetic resonance spectroscopy and restrained mo
lecular dynamics simulations. All proton signals were completely assig
ned, and interproton distances were determined using data from rotatin
g-frame nuclear Overhauser enhancement. The backbone dihedral angles w
ere deduced from measurements of coupling constants. The temperature d
ependence of the amide proton chemical shifts provided information abo
ut hydrogen bonding. Six probable solution conformations of viroisin w
ere derived from the use of distance geometry and restrained molecular
dynamics based on a set of distance constraints obtained from experim
ental data. The results of the structural analysis indicate that viroi
sin has a well ordered conformation in solution. In all these conforma
tions the functional groups essential for toxicity orient themselves i
n the same direction so as to bind to the target proteins. This featur
e is consistent with previous results about the formation of a hydroph
obic pocket on one side of the molecule. (C) Munksgaard 1994.