Expression system

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An expression system is any biological system that is able to carry out protein biosynthesis in a targeted and controlled manner, that is, to produce certain proteins based on a nucleic acid, i.e. to express them . All living cells thus represent expression systems. A distinction is made between prokaryotic and eukaryotic expression systems.

Meaning of expression systems

Expression systems are of great importance in biotechnology , where they are often used in connection with genetic engineering to obtain large quantities of recombinant proteins (e.g. insulin ). The genes that serve as blueprints for the desired proteins are inserted into a suitable expression system. The expression system “reprogrammed” in this way can then be increased and the protein isolated either from the nutrient medium or from the cell plasma after the cells have been destroyed. With these methods, the choice of the appropriate expression system is crucial, since not every protein can be produced by every organism.

Bacteria such as Escherichia coli , for example , which occur as part of the normal human intestinal flora, are suitable as expression systems for simple proteins . This has the advantage that there are fewer allergic reactions to impurities in the product if the protein is used medicinally. Bacteria are also very easy to cultivate. However, they are not suitable for all proteins because, on the one hand, they are not able to modify proteins post-translationally, i.e., unlike human cells, they cannot make the changes to the finished protein that are important for the function of the protein, on the other hand, they cannot remove many proteins from the cell, which means that they accumulate in the bacterium, clump and become unusable. In addition, human proteins formed by bacteria are usually incorrectly folded and must subsequently be natured.

Yeasts have the advantage that they perform some of these modifications and the addition mRNA of the gene litigate to what bacteria are not capable. This simplifies the reprogramming of the expression system since the gene does not have to be changed beforehand. In addition, various desired proteins can be obtained from a gene by alternative splicing . In contrast to bacteria, yeast cells can also glycosylate proteins, but this creates a different glycosylation pattern than in mammalian cells, which in the case of some proteins has a great influence on their function.

For proteins that have to have as many modifications as possible in order to be able to fulfill their function, the most suitable expression systems are those that are most similar to the system from which the gene originally originated. In the case of human proteins, mammalian cells. CHO cells ( Chinese hamster ovary ) from the ovaries of Chinese hamsters are often used here.

Each expression system has advantages and disadvantages. In general, the closer the expression system gets to the original human protein, the more demanding and laborious the system is to cultivate.

Important biotechnological expression systems

Prokaryotic
Eukaryotic

Individual evidence

  1. ^ Gerhard Richter: Practical Biochemistry. , Thieme Verlag, 2003, ISBN 978-3-13-132381-1 , p. 170.
  2. ↑ a b c Bernd Voedisch et al .: Heterologous expression of recombinant protein pharmaceuticals. In: Laborwelt, No. 3, 2005. ( Online )
  3. ^ A b Matthias W. Hentze, Andreas E. Kulozik, CR Bartram, Christian Hagemeier: Molecular Medicine: Basics, Pathomechanisms, Clinic. Gruyter Verlag, 2000, ISBN 978-3-11-015097-1 , p. 426.
  4. ↑ Michael Rolle, Anton Mayr: Medical microbiology, infection and epidemic theory. Enke Verlag, 2006, ISBN 978-3-8304-1060-7 , p. 109.
  5. ↑ David P. Clark, Nanette J. Pazdernik: Molecular Biotechnology: Fundamentals and Applications. Spektrum Akademischer Verlag, 2009, ISBN 978-3-8274-2128-9 , p. 314.
  6. ↑ Paul Präve, Uwe Faust, Wolfgang Sittig, Dieter A. Sukatsch: Handbook of biotechnology. Oldenbourg Industrieverlag, 1994, ISBN 978-3-8356-6223-0 , p. 881.
  7. ↑ Cornel Mülhardt: The Experimenter: Molecular Biology / Genomics. Spektrum Akademischer Verlag, 2008, ISBN 978-3-8274-2036-7 , p. 250.
  8. ↑ Howard Christian Peters: Transgenic inducible expression of dominant-negative KCNQ2 potassium channel subunits in the mouse brain. Tenea Verlag, 2004, ISBN 978-3-86504-034-3 , p. 10.
  9. ^ Rüdiger Wehner, Walter Gehring, Alfred Kühn: Zoologie. Thieme Verlag, 2007, ISBN 978-3-13-772724-8 , p. 400.