用改进的寡核苷酸诱导突变法将人胰岛素原基因（ＢＣＡ）删除编码Ｂ链羧端三肽（２８～３０残基）的碱基片段，得到去Ｂ链羧端三肽胰岛素原的基因（Ｂ￣（－３）ＣＡ）。为了便于表达产物的蛋白质后加工，又用ＰＣＲ的方法在Ｂ链Ｎ端起始Ｍｅｔ与Ｐｈｅ密码子之间增加了编码Ｌｙｓ的３个碱基，得到改造后基因ＬＢ￣（－３）ＣＡ。将ＬＢ￣（－３）ＣＡ克隆到表达质粒ｐＢＶ２２０上，在大肠杆菌系统中热诱导表达，表达率为１２％。表达产物经蛋白质后加工，得到的去Ｂ链羧端三肽人胰岛素（ＤＴＥＩＢ２８～３０人胰岛素）其受体活性和放免活性分别是猪胰岛素的４５％和４９％。 A modified oligonucleotide-induced mutation was used to delete the human proinsulin gene (BCA) from the base fragment encoding the B-chain carboxy-terminal tripeptide (residues 28-30) to obtain the gene for de-B chain carboxy-terminal tripeptide proinsulin (B ~ (-3) CA). In order to facilitate the protein post-processing of the expressed product, three bases encoding Lys were added between the start Met and the Phe codon at the N-terminal of the B chain by PCR to obtain a modified gene LB ~ (-3) CA. The LB ~ (-3) CA was cloned into expression vector pBV220 and induced by heat in E.coli. The expression rate was 12%. After the protein was processed, the receptor activity and radioimmunoassay of the insulin-B peptide carboxy terminal tripeptide human insulin (DTEIB28-30 human insulin) were 45% and 49% of the porcine insulin, respectively.