Protein expression

The four main in vivo expression systems used by PEF are:

Bacteria

E. coli is frequently the first expression host chosen for the production of a recombinant protein, owing to the rapid, affordable and technically straight-forward culturing associated with its use.

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Yeast

Yeast is a single-celled eukaryotic organism capable of producing very large quantities of recombinant protein. PEF offers P. pastoris as the strain of choice for yeast expression.

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Baculovirus/Insect Cell Expression Vector System (BEVS)

The Baculovirus/Insect cell expression vector system (BEVS) is a popular choice for the production of recombinant proteins, particularly those requiring complex post-translational modifications.

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Mammalian cell

Mammalian cell-based expression is the dominant system for the production of therapeutic recombinant proteins. Their capacity to handle complex post-translational modifications, folding and assembly of recombinant proteins and protein complexes is superior to other systems.

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Cell-Free

The Leishmania tarentolae extract (LTE) in vitro translation system is a rapid, convenient, flexible and cost effective tool to produce recombinant proteins for biochemical, biophysical and structural analysis (Mureev et al., 2009, Kovtun et al., 2010).

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For all protein expression services, please contact us.
To view our list of available vectors, please visit our UQ Resource Centre.

E. coli is one of the most widely used expression hosts for the production of recombinant proteins. It is often the first system chosen for producing recombinant proteins due to its advantages over other systems, such as:

  • Inexpensive setup and running costs
  • High recombinant protein production levels 
  • Short timeline from cloning to protein recovery
  • Limited technical knowledge required for culturing
  • Scalability from small (1 mL) to very large culture (>10,000 L) volumes

However, bacterial expression systems are limited in their ability to perform post-translational modifications (PTMs) and facilitate disulphide bond formation. Most proteins require some form of PTM to be produced in their native conformation. Due to the reducing environment of the bacterial cytoplasm, disulphide bond formation can only be achieved by targeting the protein to the oxidative periplasm. Some modern E. coli strains have been developed to overcome some of these limitations (see below).

Yeast are a single-celled eukaryotic organisms that combine high levels of recombinant protein production with eukaryotic post-translational modifications (PTMs). Some advantages of using yeast over other systems for protein expression include:

  • Relatively inexpensive setup and running costs
  • Very high levels of recombinant protein production
  • Able to perform many PTMs e.g. N-glycosylation
  • Simplified downstream processing for secreted proteins
  • Amenable to large-scale fermentation

The insect cell/baculovirus expression vector system (BEVS) is becoming increasingly popular for the production of recombinant proteins. The system offers a number of advantages, including:

  • Able to perform complex post-translational modifications (PTMs)
  • High success rate of soluble protein recovery
  • Suitable for the production of large protein complexes
  • High protein expression levels compared to other higher eukaryotes

The ability of insect cell/BEVS to generate proteins with complex PTMs, coupled with high expression levels, makes it particularly suitable for the production of mammalian proteins.

Insect cell/BEVS utilises the naturally occurring baculovirus, Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV), which infects insects from the Lepidopteran genus (moths and butterflies). Late in the infection cycle, the virus produces large amounts of polyhedral or inclusion bodies in the insect host, typically around 50% of the total cellular protein. This is exploited in the BEVS, where insect cells are infected with a modified AcMNPV carrying the recombinant gene of interest under control of the strong polyhedrin promoter (polh).

The dominant system to produce therapeutic recombinant proteins over the last few decades has been mammalian cell-based expression systems.

Their capacity to handle complex post-translational modifications, folding and assembly of recombinant proteins and protein complexes is superior to other systems.

Listed below are a number of articles that provide a broad overview about using different expression systems for the production of recombinant proteins.