Expression systems for the production of recombinant proteins

Recombinant proteins are proteins manufactured using recombinant DNA technology. These proteins, although they are identical to those found in natural microorganisms, are designed and produced in non-infectious expression systems, considered genetically modified organisms. These systems are used as protein-producing machines. Subsequently, the proteins produced in these organisms are purified to homogeneity, up to 95% purity, so that they can be used in in vitrodiagnosis.

Among the most common expression systems are the following:

• Bacteria. Escherichia coli is one of the most used expression system, due to its easy handling and high performance. It is a prokaryotic expression system, therefore, not recommended for the production of human proteins or proteins of microorganisms that in nature are synthesized in eukaryotic cells. This system will not be able to produce heterologous proteins with very complicated folding for several reasons: (i) they do not give rise to post-translational modifications and (ii) the reducing cytoplasm of E. colidoes not allow the formation of disulfide bridges (the possibility of producing them in the periplasm is not very robust for scaling).
• Yeasts. Pichia pastoris is the easiest to manipulate and most economical eukaryotic expression system that exists. This expression system has the ability to glycosylate proteins and generate disulfide bridges. However, its glycosylation is quite different from that used by higher eukaryotes. Sometimes, it can even give false positives due to non-specific interactions of the b (1-2) bonds present in its glycosylated residues, which is why the use of blockers is required.
• Insect cells. It is the expression system used to produce mammalian proteins that require advanced post-translational modifications. Glycosylation is similar to that of mammalian cells, although not identical. It has a generally acceptable success rate, but the protein production process is slower. It is also a significantly more expensive system.
• Mammal cells. The most common are CHO (Chinese Hamster Ovaries) and HEK293 (Human Embryonic Kidney) cells. It is the expression system used for vaccines and therapeutic proteins, since they have the capacity to carry out post-translational modifications similar to those made in humans, and are free of toxins. They are high cost, low performance and require longer production time.

Currently, at Rekom Biotech we use Escherichia coli and Pichia pastoris as an expression system for the production of recombinant proteins. In the future, we will introduce the rest of the expression systems. Take a look at our portfolio and do not hesitate to contact us! We will be happy to help you.