Methods The Ecs gene was cloned using overlap extension PCR and the condon of Met28 was mutated to Leu. Three pieces of Ecs genes were linked in the same orientation and inserted into expression vector pET30a. The recombinant plasmid was expressed in E.

• 方法:采用重叠延伸PCR克隆Ecs基因；将第28位Met的密码子突变为Leu；利用其序列特点及酶切位点；在表达载体pET30a上将Ecs基因以同向串联方式连接；在E.