[Research of a screening strategy for high prokaryotic expression clone]

The low expression in E. coli can be often explained by the beginning sequence that causes low translational initiation. A simple selection procedure is then used to enrich those sequences from the bank that lead to high levels of translation. The selection procedure is based on the use of a translationally coupled tetracycline resistance gene. The basic steps are as follows: (1) Construction of selection vector pBV223; (2) Screening high expression clones through different tetracycline concentrations. Several clones have been selected in 60 microg/ml concentration of tetracycline. So this system will provide an important way in preparation of some cytokines which have a low expression level in E. coli but have significant economic value.