An Insect Cell-Free System for Recombinant Protein Expression Using cDNA Resources

The Transdirect insect cell is a newly developed in vitro translation system for mRNA templates, which utilizes an extract from cultured Spodoptera frugiperda 21 (Sf21) insect cells. An expression vector, pTD1, which includes a 5′-untranslated region (UTR) sequence from a baculovirus polyhedrin gene as a translational enhancer, was also developed to obtain maximum performance from the insect cell-free protein synthesis system. This combination of insect cell extract and expression vector results in protein productivity of about 50 μg per mL of the translation reaction mixture. This is the highest protein productivity yet noted among commercialized cell-free protein synthesis systems based on animal extracts.