Solution conformation of leiurotoxin I (scyllatoxin) by 1H nuclear magnetic resonance. Resonance assignment and secondary structure.

A proton NMR study at 500 MHz of leiurotoxin I in water is presented. Nearly complete sequence-specific assignments of the individual backbone and side-chain proton resonances were achieved using through-bond and through-space connectivities obtained from standard two-dimensional NMR techniques. The secondary structure of this toxin is inferred from a combination of short-range nuclear Overhauser enhancements, scalar couplings and proton/deuteron exchange rates. Three disulfide bridges locate the N-terminal part (that is alpha-helical from residue 6 to 16) on one side of a C-terminal two stranded antiparallel beta sheet (from Leu18 to Val29). The latter features a tight turn at Gly23-Asp24.