Solid state and solution conformation of [Ala7]-phalloidin: a synthetic phallotoxin analogue.
Phallotoxins are toxic compounds produced by poisonous mushroom Amanita phalloides and belong to the class of bicyclic peptides with a transannular thioether bridge. Their intoxication mechanism in the liver involves a specific binding of the toxins to F-actin that, consequently, prevents the depolymerization equilibrium with G-actin. Even though the conformational features of phallotoxins have been worked out in solution, the exact mechanism of interaction with F-actin is still unknown. In this study a toxic phalloidin synthetic derivative, bicyclo(Ala1-D-Thr2-Cys3-cis-4-hydroxy-Pro4-Ala5-2-mercapto-Trp6-Ala7)(S-3-->6) has been synthesized. A substitution at position 7. with an Ala residue replaces the 4,5-dihydroxy-Leu present in the natural phalloidin. This analogue has formed crystals suitable for X-ray analysis, and represents the first case for such a class of compounds. The solid-state structure as well as the solution conformation have been evaluated. NMR techniques have been used to extract interproton distances as restraints in subsequent molecular dynamics calculations. Finally, a direct comparison between structures in solution and in the solid state is presented.
Zanotti
G
G
Dipartimento di Chimcia, Università di Napoli Federico II, Complesso Universitario Monte S. Angelo, Italy. paolillo@chemistry.unina.it
Falcigno
L
L
Saviano
M
M
D'Auria
G
G
Bruno
B M
BM
Campanile
T
T
Paolillo
L
L
D000199:Actins / Q000737:chemistry; D000545:Amanita / Q000737:chemistry; D000546:Amanitins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004121:Dimethyl Sulfoxide; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010590:Phalloidine / Q000031:analogs & derivatives / Q000737:chemistry*; D017433:Protein Structure, Secondary
D000199:Actins; C430290:Ala(7)-phalloidin; D000546:Amanitins; D010590:Phalloidine; D004121:Dimethyl Sulfoxide