Recombinant ??-Conotoxin MVIIA Possesses Strong Analgesic Activity

Abstract

omega-Conotoxin (CTX) MVIIA is a specific antagonist of N-type voltage-sensitive calcium channels. A synthetic peptide version of CTX MVIIA (ziconotide) has been approved by the US FDA for severe and chronic pain. Given the high cost and complexity of the synthetic process of the disulfide-rich peptide, the genetic recombinant approach may simplify the development of this potent therapeutic agent. In this study, we report a new method for production of the recombinant CTX MVIIA. A novel DNA fragment encoding CTX MVIIA was designed using Escherichia coli-preferred codons, and the fragment was cloned into the expression vector pGEX(2T). The fusion protein, CTX MVIIA and glutathione-S-transferase (GST) [GST-CTX MVIIA], was expressed in E. coli and purified by affinity chromatography on a glutathione-agarose column. After digestion with thrombin, the CTX MVIIA fragment was purified on a Sephacryl S-100 HR column and identified by mass spectrometry. The bioactivity of the peptide was evaluated by the hot tail-flick assay, in which the CTX MVIIA was intracerebroventricularly administered into Sprague-Dawley rats and its antinociceptive effect measured. The analgesic activity of the conotoxin was about 800 times stronger than that of morphine. The recombinant CTX MVIIA expressed in E. coli has shown marked analgesic activity, which may have potential in clinical application.