牛凝乳酶全长cDNA的克隆及其原核表达载体的构建

从小牛皱胃中提取凝乳酶(Chymosin)总RNA,经过RT-PCR获得凝乳酶cDNA,纯化后与pMD-18T载体连接,转化大肠杆菌JM109,通过双酶切和序列测定,获得了凝乳酶全长基因序列。序列测定表明,凝乳酶全长核苷酸长度为1 143 bp,编码381个氨基酸。与GenBank上已发表序列NM_180994进行比较,核苷酸同源性为99.56%。将该基因片段克隆到原核表达载体pET-22b中,构建重组质粒pET-22b/Chymosin,所获重组质粒经过酶切、测序鉴定,证实含有目的片段,且连接、构建正确,为凝乳酶的进一步表达奠定了基础。

Cloning and Prokaryotic Expression Vector Construction of Bovine Chymosin

In this study,the total RNA of chymosin was extracted from Absomum of calf and its cDNA was obtained by RT-PCR.The purified RT-PCR products and pMD-18T vector were ligated and transformed into host strain E.coli JM109.The full length of Chymosin gene is consist of 1 143 bp,and encodes 381 amino acids.The homology of the nucleotides with NM180994 is 99.56%.The aim gene was expression on the prokaryotic expression vector pET-22b and a recombinant plasmid pET-22b/Chymosin was constructed successfully.