What factors should I consider when choosing protein expression systems?

Factors to consider when choosing protein expression systems include: structural complexity, post-translational modifications, solubility. The structural complexity of a protein may indicate which system is most suitable for recombinant generation. For example, a bacterial expression system is the best choice for generation of a recombinant protein that is a prokaryote. Eukaryotic proteins with tertiary and/or quaternary structures work best with a mammalian or insect expression system. Solubility is important because different host organisms have carrying capabilities to produce soluble proteins. It is important to choose an expression system that is more suited to produce the protein in its native state. Post translational modifications (PTMs) can be vital for a protein’s function, folding, and localization. Bacteria lack many PTMs that eukaryotes have. As a result, expression of a eukaryotic protein in bacteria may yield a misfolded and/or inactive product. Mammalian cell expression systems possess the most sophisticated PTM pathways, and are the optimal choice when generating a eukaryotic protein that requires PTMs for its function and folding. Additional factors to consider include purification speed, and yield.