The invention provides a nucleic acid sequence comprising a sequence of contiguous nucleotides, wherein said sequence of contiguous nucleotides has at least 90% sequence identity to the nucleic acid sequence of SEQ ID NO: 1, and wherein said sequence of contiguous nucleotides encodes a single-chain BoNT/E1 protein. The present invention also provides methods for producing soluble single-chain BoNT/E1 protein in an E. coli host cell, together with methods for producing soluble di-chain BoNT/E1 protein.本發明提供一種包含連續核苷酸之序列的核酸序列，其中該連續核苷酸之序列與SEQ ID NO：1之核酸序列具有至少90%之序列一致性，且其中該連續核苷酸之序列編碼單鏈BoNT/E1蛋白。本發明亦提供在大腸桿菌(E.coli)宿主細胞中產製可溶性單鏈BoNT/E1蛋白之方法以及產製可溶性雙鏈BoNT/E1蛋白之方法。
