Sequence-specific Assignment of (1)H-NMR Resonance and Determination of the Secondary Structure of HWTX-II.

Huwentoxin-II (HWTX-II)is an insecticidal peptide purified from the venom of spider Selenocosmia huwena. The structure of this toxin in solution was investigated using 2D-NMR. The complete sequence-specific assignments of proton resonance in the (1)H-NMR spectra of HWTX-II were obtained by analyzing a series of 2D spectrum, including COSY, DQF-COSY, TOCSY and NOESY. All the backbone protons and side chain protons, except epsilonNH(2) protons of Lys residues, were identified by d(alphaN), d(alpha&dgr);, d(NN) and d(betaN) connectivities. The results provide a basis for further determination of the solution conformation of HWTX-II. Furthermore the secondary structure of HWTX-II was determined from NMR data. It contained mainly extended conformation, especially a double-stranded anti-parallel beta-sheet with Trp27--Cys29 and Cys34--Lys36 at the C terminal, and it lacked helix. These characters of the secondary structure of HWTX-II were similar to those spider toxins which structure in solution had been reported.