- The target cell into which the foreign DNA is to be introduced is referred to as the host cell.
The host system
The choice of the host system depends on the objective of the experiment. Structural studies or the industrial mass production of a certain prokaryotic gene product require a simple prokaryotic host system that is as easy to handle as possible. Similar studies and syntheses of eukaryotic gene products can only be carried out to a very limited extent in prokaryotic host systems, since eukaryotic proteins are for the most part post-translationally modified and prokaryotic cells do not have such modification systems.
A typical example of this problem is insulin, which has been produced on an industrial scale for several years. Mature insulin consists of two polypeptide chains linked by two disulfide bridges. The im EscherichiacoliInsulin synthesized in the expression system must be processed enzymatically as a pre-hormone for the formation of the disulfide bridges. An insulin produced in the yeast expression system does not require this enzymatic post-treatment.
Expression studies of eukaryotic genes can only be carried out in eukaryotic host systems due to the significantly higher complexity of the genetic apparatus compared to prokaryotic systems.