[Synthesis and oxidative refolding of an N-terminal truncate of jingzhaotoxin-V and characterization of its activities of sodium channels].

An N-terminal tyrosine residue truncate of Jingzhaotoxin-V (Y1-JZTX-V) was synthesized by solid-phase chemical methods using Fmoc-protected amino acids. Reversed-phase high performance liquid chromatography (RP-HPLC) and matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/TOF MS) were used to monitor the oxidative refolding of Y1-JZTX-V to find the optimal renaturation conditions of the synthetic linear peptide. When Y1-JZTX-V (0.05 mg/L) was dissolved in 0.1 mol/L Tris-HCl buffer containing 1 mmol/L GSH and 0.1 mmol/L GSSG at pH 7.50 and 4 degrees C, the best renaturation yield of the truncate toxin was obtained. Under the whole-cell patch-clamp mode, Y1-JZTX-V could inhibit tetrodotoxin-resistant (TTX-R) and tetrodotoxin-sensitive (TTX-S) sodium currents in adult rat dorsal root ganglion neurons with IC50 values of 160 nmol/L and 39.6 nmol/L, respectively. The inhibition potentiality of Y1-JZTX-V on TTX-S sodium currents was almost the same as the natural JZTX-V, while that on TTX-R sodium currents was obviously weakened. The IC50 value of Y1-JZTX-V on TTX-R sodium currents was 5.8 times as many as that of natural JZTX-V. Present findings indicated that the first tyrosine residue (Y1) in the N-terminal of JZTX-V was involved in the binding activities of JZTX-V to TTX-R sodium channels.