The efficient production of proteins via expression of recombinant genes in cells other than those that naturally produce the protein has been critical to the study and the therapeutic utility of a wide variety of proteins.E. coliexpression systems are useful for many proteins. However, large complex proteins are not expressed efficiently in bacteria. Also, bacterial expression cannot be used for eukaryotic proteins that require glycosylation for their activity. Some established animal cell lines can be used as production hosts since they are easily transfected, can grow to high cell densities, and can be propagated in low-serum or serum-free medium.
