Protein Expression

E. coli is frequently the first expression host chosen for the production of a recombinant protein, owing to the rapid, cheap and technically straight-forward culturing associated with its use. Services available from PEF include:

• Developing an effective strategy for molecular cloning and bacterial expression
• Custom or high throughput cloning into a range of bacterial expression vectors, including:
  • pOPIN
  • pET
  • pGEX
• Transformation into a wide range of E. coli expression strains, including:
  • BL21 (DE3)
  • BL21 (DE3) pLysS
  • BL21 (DE3) CodonPlus-RIL
  • BL21 (DE3) Star
  • Rosetta (DE3) pLysS
  • Rosetta 2 (DE3)
  • Arctic Express (DE3) pLysS
  • Tuner (DE3)
  • Shuffle T7 Express
• Small-scale expression screening to determine optimal expression conditions
• Large-scale expression in shake flasks and stirred-tank bioreactors

In addition to regular communication updates throughout your project, we provide a highly detailed report on project completion. To view a sample report, please download the pdf here.

For all bacterial expression services, including customised cloning and bioreactor-scale expression, please contact us for a quote.

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).

Bacterial Expression Hosts

A wide range of bacterial strains are available for recombinant protein production, each offering a novel advantage. The most common strains carry a DE3 lysogen that enables expression of T7 RNA polymerase, driving high level expression of proteins under control of the T7 Promotor in the vector. In these systems, recombinant protein expression is repressed by the host strain (and by the vector if using pET) until induction with IPTG.

Another feature common in a range of host strains is pLysS. pLysS is a plasmid carrying a gene encoding T7 phage lysozyme, an inhibitor of T7 RNA polymerase. This system enables tighter control over protein expression and is particularly useful for the production of toxic genes, or if expression is observed prior to induction ('leaky' expression).

Some common E. coli expression strains are listed below.

Strain	Features
BL21 (DE3)	Most common host strain, enables high-level recombinant protein expression
BL21 (DE3) pLysS	Enables high-level expression and suppression of T7 RNA Polymerase basal level expression
BL21-CodonPlus	Improved expression of genes with codons rarely used in bacteria
Rosetta	Improved expression of genes with codons rarely used in bacteria
Arctic Express	Contains a plasmid encoding chaperonins to aid in folding and allow expression at low temperature (12°C)
Tuner	Enables uniform uptake of IPTG into each cell, finer control of expression can be achieved by varying IPTG concentration
Shuffle® T7 Express	Expresses DsbC to enable cytoplasmic disulphide bond formation

Optimising Expression in Bacteria

Generating soluble, active protein is a major challenge for recombinant protein production in E. coli. Over-expression of eukaryotic proteins often leads to the formation of insoluble aggregates known as inclusion bodies. Although proteins in inclusion bodies are generally of a very high yield and purity, the material must be denatured and refolded to restore native protein structure.

Several methods have been developed to combat the formation of inclusion bodies and drive soluble protein expression. Some of these are described briefly below.

Host strain selection

Selection of the right cell strain is critical for successful soluble protein production. Advances in host cell engineering have led to the development of several key capabilities that should be taken into consideration when choosing a strain for expression:

• Rare codon usage: These strains carry an extra plasmid (e.g. pRARE) that encode a number of rare codon tRNAs. This allows more efficient expression of genes that contain these rare codons (generally those of eukaryotic origin)
• Improved folding: These strains carry either a mutation in specific genes that inhibit the formation of disulphide bonds, or carry a chromosomal copy of disulphide bond isomerase. This enables cytoplasmic production of proteins requiring disulphide bonds
• Induction control: These strains contain a mutation in the lac permease, allowing homogenous uptake of IPTG into all cells in the culture. This enables finer control over induction by varying the concentration of IPTG

Growth temperature

Although most bacterial strains are typically cultured at 37°C, lowering the temperature (e.g. to 30°C or 15°C) often improves protein folding and increases soluble protein production.

Expression with a fusion tag

Fusion partners such as affinity or solubility tags can have a significant effect on the recovery of a protein. There are several solubility tags that are commonly used to improve soluble protein expression, including maltose binding protein (MBP), glutathione S-transferase (GST), thioredoxin (Trx) and small ubiquitin-like modifier (SUMO).

Co-expression

Co-expression of recombinant proteins with chaperonins and foldases can aid expression in multiple ways. Chaperonins such as cpn10 and cpn60 bind to and stabilise unfolded or partially folded proteins. Expression with foldases such as disulphide oxioreductase (DsbA) or disulphide isomerase (DsbC) can aid in producing soluble protein if formation of disulphide bonds is required.

Codon optimisation

Codon optimisation is the process of modifying codons in a gene sequence to match the codon usage bias of the host cell used for expression. This is frequently applied to heterologous proteins expressed in E. coli, as codon usage varies heavily between prokaryotes and eukaryotes. Software is used to optimise the codon sequences, followed by gene synthesis.

Media

LB broth is the most commonly used media for cloning and bacterial expression. Although this media is simple and cheap to prepare, it does not support high-level biomass production. Other media formulations such as TB, 2YT or chemically defined media enable higher density cultures in shake flasks and bioreactors.

Antibiotics

Antibiotics enable selection of recombinant clones as well as preventing contamination during cloning and expression. However, the use of antibiotics in large-scale expression is often decreased or omitted, due to the associated costs. Antibiotic selection pressure also increases the metabolic burden on the cell, impacting recombinant protein expression.

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. Services available from PEF include:

• Developing an effective strategy for molecular cloning and yeast expression
• Custom or high throughput cloning into a range of yeast expression vectors, including:
  • pPink-αHC
  • pPICZα-A,B,C
  • pPICZ-A,B,C
  • pHIL-S1
• Transformation into a range of P. pastoris strains, including:
  • PichiaPink^TM (strains 1 to 4)
  • GS115
  • X-33
  • KM71H
• Small-scale expression screening to determine optimal expression conditions
• Large-scale expression in shake flasks and stirred-tank bioreactors

For all yeast expression services, including customised cloning and bioreactor-scale expression, please contact us for a quote.

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

Yeast Expression Hosts

There are two strains commonly used for protein production in yeast: Saccharomyces cerevisiae and Pichia pastoris.P. pastoris has a number of advantages over S. cerervisiae that make it the preferred host cell for expression: a strong, inducible promoter, high growth rates and PTM patterns more similar to higher eukaryotes.

P. pastoris is a methylotrophic yeast, capable of using methanol as the sole source of carbon. In the presence of methanol, the alcohol oxidase gene (AOX1) is highly up-regulated and can account for up to 30% of total cell protein. Current expression systems exploit this feature and use the AOX1 promoter to drive recombinant protein expression in the presence of methanol.

P. pastoris does not secrete many native proteins. Consequently, by using the alpha-mating factor secretion signal peptide and exploiting the secretory pathway, downstream processing can be greatly simplified. Secreting recombinant proteins also avoids the need to disrupt the tough yeast cell wall for release of intracellular proteins.

Some common P. pastoris expression strains are listed below.

Strain	Features
PichiaPink Strain 1	Adenine auxotroph
PichiaPink Strain 2	Adenine auxotroph, Protease A knockout
PichiaPink Strain 3	Adenine auxotroph, Protease B knockout
PichiaPink Strain 4	Adenine auxotroph, Protease A and Protease B knockout
X-33
GS115r	Histidine auxotroph
KM71H	Strain uses weaker AOX2 promoter

Some vectors commonly used for expression in P. pastoris are listed below.

Strain	Selection	Features
pPink-αHC	Nutrient-based (Adenine)	Complements ade2 deletion, secretion via α-mating factor
pPICZα-A,B,C	Zeocin	Secretion via α-mating factor, 6xHis and C-myc C-term tags
pPICZ-A,B,C	Zeocin	6xHis and C-myc C-term tags
pHIL-S1	Nutrient-based (Histidine)	Complements HIS4 deletion, secretion via PHO1 secretion signal

Post-translational Modifications (PTMs)

Yeast are capable of performing a basic subset of PTMs including N-glycosylation, the most common modification. The N-glycan structures produced by yeast are less complex compared to higher eukaryotic systems (e.g. insect and mammalian cells), and contain large amounts of mannose. These high mannose structures can be removed with the aid of enzymes such as N-Glycosidase F (PNGase).

Recent advances in genetic engineering have led to the development of yeast strains that produce mammalian-like N-glycosylation structures. These strains carry a relatively large subset of genes of mammalian origin that aid in building more complex structures and trafficking of the modifying enzymes within the cell.

The insect cell/baculovirus expression vector system (BEVS) is a popular choice for the production of recombinant proteins, particularly those requiring complex post-translational modifications. Services available from PEF include:

• Developing an effective strategy for molecular cloning and insect cell/BEVS expression
• Custom or high throughput cloning into a range of baculovirus transfer vectors, including:
  • pFastbac-1
  • pFastBac Dual
  • pBac-1
  • pENTR
• Small-scale expression screening to determine optimal expression conditions
• Large-scale expression in shake-flasks and WAVE bioreactor

PEF offers the following systems to produce recombinant proteins using insect cell/BEVS:

• Bac-to-Bac
• flashBAC
• BaculoGOLD
• BaculoDirect

In addition to regular communication updates throughout your project, we provide a highly detailed report on project completion. To view a sample report, please download the pdf here.

For all insect cell/BEVS expression services, including customised cloning and bioreactor-scale expression, please contact us for a quote.

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).

Insect Cell/BEVS Expression Systems

There are a number of different systems that can be used to generate a recombinant baculovirus containing the gene of interest. Some of the more common systems are listed below.

System	Transfer Vectors	Features
Bac-to-Bac	pFastbac-1, pFastBac Dual	Requires integration with baculovirus shuttle vector (Bacmid) in bacterial host cell before transfection
flashBAC	pBac-1	Transfection with linear DNA, recombination occurs within host insect cells. Deletion of chiA enables better secretion of recombinant protein
BaculoGOLD	pVL1392, 1393	Transfection with linear DNA, recombination occurs within host insect cells
BaculoDirect	pENTR	Transfer vector recombines with linear DNA before transfection into host cell. Requires Ganciclovir as selection agent

Cell Lines

The most common cell lines for use in the BEVS are Sf9 and High Five^TM. Both can be grown as adherent or suspension cultures and scaled up from microplates in a high throughput format to shake flasks and WAVE bioreactors. They are also able to be grown in serum-free media (SFM) and do not require the additon of CO₂ gas.

Some commonly used insect cell lines are listed below.

Cell Line	Origin	Features
Sf9	Spodoptera frugiperda	Adapted to SFM, commonly used to express all types of recombinant proteins
Mimic Sf9	Spodoptera frugiperda	Adapted to SFM, expresses mammalian glycosyltransferases to generate proteins with more complex N-glycan structures
High FiveTM	Trichoplusia ni	Adapted to SFM, commonly used for secretion of recombinant proteins

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. Services available from PEF include:

• Developing an effective strategy for molecular cloning and mammalian expression
• Custom or high throughput cloning into a range of mammalian expression vectors, including:
  • pcDNA3.1
  • pcDNA3.3
  • pOPIN series
• Transient transfection into CHO or HEK-293 cell lines
• Stable pool selection and expression
• Small-scale transient expression screening to determine optimal expression conditions
• Large-scale transient expression in shake flasks and WAVE bioreactor

For all mammalian expression services, including customised cloning and bioreactor-scale expression, please contact us for a quote.

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.

Cell Lines & Media

Traditional media formulations for mammalian cell culture relied on the addition of animal-serum from 1% to 20% of the total culture volume. However serum-free media has become the more popular choice driven principally by concerns about the introduction of adventitious agents in animal derived serum and the expense. Serum-free media formulations have been shown to perform equally as well as serum supplemented media.  Host cell lines have also been improved to enhance their ability to survive, grow and produce recombinant proteins, in culture. Introduction of antiapoptotic, growth factor, proto-onco and cell-cycle control genes into host cell lines have been shown to greatly enhance their capabilities. Commercially available cell lines carry many of these genetically engineered enhancements. Commonly used mammalian cell lines for protein production, in particular biotherapuetics are the Chinese hamster ovary (CHO), Human embryonic kidney (HEK-293) and Mouse myeloma (NS0) cell lines.

Expression Vectors

Mammalian expression vectors have been engineered to contain elements that improve expression and are generally more complex than vectors from other systems. Some common variable elements found in expression vectors are listed below:

• Strong viral promoters and enhancers for recombinant protein expression

• Alternate (sometimes weaker) promoter/enhancer for the selective gene

• An intron sequence to enable splicing (Splicing has been shown to promote mRNA nuclear export)

• Unique linearisation site (known to decrease disruption of the expression cassette during integration)

• Directed integration into the host cell genome via a recombination system e.g. Cre/loxP

Transient vs Stable Cell Culture

There are two main methods for recombinant protein production in mammalian cells i.e. stably transfected and transiently transfected cell lines. Stably transfected cell lines enable continuous expression of the recombinant protein and have been shown to produce high yields.  The creation of a stable cell line can take up to several months to complete.

A transient transfection can be used for small- to large-scale expression cultures. Recent improvements to the method have been able to increase yields from milligram to gram quantities. The advantages of a transient transfection method lie in the shorter timeframe from DNA delivery to protein harvest.

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).

pLTE Products and Services offered through PEF:

 

Product/Service	Description	Available from
Cell-free Protein Expression Kit (Plasmid Based) - 70 reactions	Translational competent LTE cell extract - LTE cell extract (1ml) pLTE expression vector - 9 µg	Please enquire
Cell-free Protein Expression Kit (PCR Based) - 70 reactions	Translational competent LTE cell extract - LTE cell extract (1ml) Species independent translation sequence (SITS) fragment - 600 ng Forward primer for overlap extension PCR - 50 µl of 10 µM  pLTE (EGFP control) vector - 9 µg	Please enquire
pLTE vectors	PEF offers 5 different vectors: pLTE (EGFP control) pLTE_6H_EGFP_3C pLTE_3C_EGFP_6H pLTE_6H_N and pLTE_6H_C More info on vectors...	Please enquire
Plasmid-based Cloning with Optional Cell-free Expression	Order cloning and small-scale expression testing via the PEF Resource Centre. Cell-free vectors available: pLTE_6H_EGFP_3C pLTE_3C_EGFP_6H pLTE_6H_N and pLTE_6H_C More info on vectors...	Resource Centre
PCR-based Cloning with Expression Screening	Order cloning with Expression Screening via the Template Design Shop.	Resource Centre
Related Manuals: Plasmid based LTE Cloning manual (pdf) PCR based LTE Cloning manual (pdf)

 

Leishmania tarentolae extract (LTE) Cell-Free Technology is a novel in vitro protein production system developed in the group of Prof. Kirill Alexandrov at the Institute for Molecular Biosciences (The University of Queensland). The system is based on the translation competent extracts of protozoan L. tarentolae.

 

Why Leishmania?

Leishmania is easy to grow in bioreactors like a prokaryote (such as E.coli), but is a non-pathogenic eukaryote with eukaryotic protein translation and folding machinery. Also, all endogenous message mRNAs in Leishmania carry an identical leader sequence, allowing a single antisense oligonucleotide to suppress translation of new unwanted endogenous Leishmania proteins in the lysate.
 

How it works:

The system is remarkably simple and allows single step production of recombinant protein from either plasmid or PCR-generated DNA templates. The system uses coupled transcription/translation; hence the lysate also contains enzymes and components necessary for conversion of introduced DNA into mRNA, which then codes for the desired protein.  LTE technology enables the production of difficult-to-express proteins rapidly and in a multiplexed format. PEF supplies bulk LTE lysate and provides template design and cloning services. Custom expression of genes in the cell-free system can also be performed.

 

pLTE Vectors:

The pLTE expression vectors are designed to be used in conjunction with the Leishmania tarentolae extract (LTE) in vitro translation system.

PEF offers 5 different vectors:

1. pLTE (EGFP control)

2. pLTE_6H_EGFP_3C

3. pLTE_3C_EGFP_6H

4. pLTE_6H_N and

5. pLTE_6H_C

pLTE (EGFP control), pLTE_6H_EGFP_3C and pLTE_3C_EGFP contain an EGFP gene, which can be used as a positive control for transcription/translation reactions. pLTE_6H_N and pLTE_6H_C do not contain an EGFP gene. All vectors except the pLTE (EGFP control) contain a 6xHis-tag.

Additionally, all the vectors have a species independent translational sequence (SITS) incorporated upstream of the EGFP ORF. SITS consists of a poly(UUUUA)₁₃ 5′ UTR fused to a sequence which forms three mRNA stem-loop structures (Mureev et al., 2009). Translation of this sequence results in 17 additional amino acids at the N’ terminus of the target protein. This configuration ensures the highest yield of recombinant protein synthesis in the LTE and all other cell free expression systems.

You can choose to clone the gene of interest into the pLTE (EGFP control) vector via three cloning strategies:

1. Replacement of EGFP control gene by target gene

2. Fusion of target gene to N’ of EGFP gene

3. Fusion of target gene to C’ of EGFP gene

Applications of LTE Expression System

The system is most generally suitable for applications where small amounts of difficult to express proteins (in other systems) are required.

• Co-expression of multiple genes for production of protein complexes

• Rapid protein engineering (truncations, insertions and site directed mutagenesis)

• Construction of complete expressed proteomes

• Functional deorphanization of genomes

• Expression of difficult proteins (for instance malaria –derived proteins)

• Expression of membrane proteins

• Production of proteins for protein microarrays

Advantages of LTE Expression

• Cost efficient high throughput expression

• Eukaryotic protein folding

• Low cost

• Single tube format

• Scalability

• Effective incorporation of unnatural amino acids

Listed below are a number of articles that provide a broad overview about using different expression systems for the production of recombinant proteins. Jump to each section by clicking the link below:

Bacteria - Yeast - Insect-cell/BEVS - Mammalian-cell - In Vitro

Bacterial expression system

Papaneophytou, C.P. et al. Statistical approaches to maximize recombinant protein expression in Escherichia coli: A general review. Protein Expression and Purification 94, 22–32 (2014) Link

Kudla, G. Coding-Sequence Determinants of Gene Expression in Escherichia coli. Science 324, 255-258 (2014) Link

Muntari, B., et al. Recombinant bromelain production in Escherichia coli: process optimization in shake flask culture by response surface methodology. AMB Express 2:12 (2012) Link

Rouet, R., et al. Expression of high-affinity human antibody fragments in bacteria. Nature Protocols 364VOL.7 NO.2 (2012) Link

Vincentelli, R. et al. High-throughput protein expression screening and purification in Escherichia coli, Methods 55, 65-72 (2011) Link

Unger, T., et al. Applications of the Restriction Free (RF) cloning procedure for molecular manipulations and protein expression. Journal of Structural Biology 172, 34-44 (2010). Link

Schein, C.H. Soluble Protein Expression in Bacteria. Encyclopedia of Industrial Biotechnology: Bioprocess, Bioseparation, and Cell Technology 1-20 (2010).

Francis, D.M. et al. Strategies to Optimize Protein Expression in E. coli. Current protocols in protein science Chapter 5, Unit 5 24 (2010). Link

Brondyk, W.H. Selecting an Appropriate Method for Expressing a Recombinant Protein. Guide to Protein Purification, Second Edition 463, 131-147 (2009). Link

Rosano G.L. et al. Rare codon content affects the solubility of recombinant proteins in a codon bias-adjusted Escherichia coli strain. Microbial Cell Factories 8:41 (2009) Link

Selleck, W. et al. Recombinant protein complex expression in E. coli. Current protocols in protein science Chapter 5, Unit 5 21 (2008). Link

Komar A.A A pause for thought along the co-translational folding pathway. Trends in Biochemical Sciences Vol.34 No.1 (2008) Link

Berrow, N.S. et al. A versatile ligation-independent cloning method suitable for high-throughput expression screening applications. Nucleic Acids Research 35, e45 (2007). Link

Cabrita, L.D., et al. A family of E. coli expression vectors for laboratory scale and high throughput soluble protein production. BMC Biotechnology 6, 12 (2006). Link

Duetz, W.A., et al. Methods for Intense Aeration, Growth, Storage, and Replication of Bacterial Strains in Microtiter Plates. Applied and Environmental Microbiology, Vol 66, No. 6, 2641–2646 (2006) Link

Waugh, D. Making the most of affinity tags. TRENDS in Biotechnology Vol.23 No.6 (2005) Link

Goulding C.W. et al. Protein production in Escherichia coli for structural studies by X-ray crystallography. Journal of Structural Biology 142 133–143 (2003) Link

 

Yeast expression system

Spadiut, O. et al. Microbials for the production of monoclonal antibodies and antibody fragments. Trends in Biotechnology 1:54-60 (2014) Link

Vogl, T. et al. New opportunities by synthetic biology for biopharmaceutical production in Pichia pastoris. Current Opinion in Biotechnology 6:1094-101 (2013) Link

Jiang Y. et al. Purification process development of a recombinant monoclonal antibody expressed in glycoengineered Pichia pastoris. Protein Expression and Purification 76 7–14 (2011) Link

Abad, S. et al. Stepwise engineering of a Pichia pastoris D-amino acid oxidase whole cell catalyst. Microbial Cell Factories, 9:24 (2010) Link

Bollok, M., Resina, D., Valero, F. & Ferrer, P. Recent patents on the Pichia pastoris expression system: expanding the toolbox for recombinant protein production. Recent Patents on Biotechnology 3, 192-201 (2009). Link

Cregg, J.M. et al. Expression in the yeast Pichia pastoris. Methods in Enzymology 463, 169-189 (2009). Link

Gong B. et al. Characterization of N-Linked Glycosylation on Recombinant Glycoproteins Produced in Pichia pastoris Using ESI-MS and MALDI-TOF. Methods in Molecular Biology, Glycomics: Methods and Protocols, vol. 534 Chapter 16 (2009) Link

Ghosalkar A. et al. Optimization of chemically defined medium for recombinant Pichia pastoris for biomass production. Bioresource Technology 99 7906–7910 (2008) Link

Hamilton, S.R. & Gerngross, T.U. Glycosylation engineering in yeast: the advent of fully humanized yeast. Current Opinion in Biotechnology 18, 387-392 (2007). Link

Lin-Cereghino, J., et al., Condensed protocol for competent cell preparation and transformation of the methylotrophic yeast Pichia pastoris. Biotechniques 38(1): 44–48. (2005)  Link

Suga M. et al. Cryopreservation of competent intact yeast cells for efficient electroporation. Yeast 16: 889-896. (2000) Link

 

Insect cell / BEVS expression system

Fernandes, F. et al. Insect cells as a production platform of complex virus-like particles Expert Rev. Vaccines12(2), 225–236 (2013) Link

Kost, T. Baculovirus Gene Delivery: A Flexible Assay Development Tool. Current Gene Therapy 10 168-173 (2010) Link

Airenne, K.J., et. al. In Vivo  Application and Tracking of Baculovirus. Current Gene Therapy, 2010 Link

Madhan, S. et al. Baculovirus as Vaccine Vectors. Current Gene Therapy 10 201-213 (2010) Link

Trowitzsch, S., et al.  New baculovirus expression tools for recombinant protein complex production. Journal of Structural Biology 172, 45-54 (2010). Link

Aucoin, M.G., et al.  Bioprocessing of baculovirus vectors: a review. Current Gene Therapy 10, 174-186 (2010). Link

Jarvis, D.L. Baculovirus-insect cell expression systems. Methods in Enzymology 463, 191-222 (2009). Link

Chung Y.C., et al., Expression, purification and characterization of enterovirus-71 virus-like particles. World J Gastroenterol; 12(6): 921-927 (2006) Link

Kost, T.A., et al.  Baculovirus as versatile vectors for protein expression in insect and mammalian cells. Nature Biotechnology 23, 567-575 (2005). Link

Weber, W. Optimisation of protein expression and establishment of the Wave Bioreactor for Baculovirus/insect cell culture. Cytotechnology 38: 77–85, (2002) Link

 

Mammalian cell expression system

Almo S.C., et al. Better and faster: improvements and optimization for mammalian recombinant protein production. Current Opinion in  Structural Biology. 26:39-43 (2014) Link

Bandaranayake A.D. et al. Recent advances in mammalian protein production. FEBS Letters. 588 2 253-60 (2014) Link

Zhang, J. Mammalian Cell Culture for Biopharmaceutical Production. Fermentation and Cell Culture Chapter 12 157-178 (2012) Link

Baldi. L., et al. Large-scale transfection of mammalian cells. Methods in Molecular Biology Volume 801 13-26 (2012) Link

Rodrigues, M.E. Technological Progresses in Monoclonal Antibody Production Systems. Biotechnol. Prog. Vol. 26, No. 2 (2010) Link

Hacker D.L. 25 years of recombinant proteins from reactor-grown cells—Where do we go from here? Biotechnology Advances 27 1023–1027 (2009) Link

Nettleship, J. et al., The Production of Glycoproteins by Transient Expression in Mammalian Cells. Methods in Molecular Biology: High Throughput Protein Expression and Purification, vol. 498 Chapter 16 (2009) Link

Lackner, A. A bicistronic baculovirus vector for transient and stable protein expression in mammalian cells. Analytical Biochemistry 380 146–148 (2008) Link

Matasci, M. et al. Recombinant therapeutic protein production in cultivated mammalian cells:current status and future prospects. Drug Discovery Today: Technologies 5, e37-e42 (2008). Link

Baldi, L., et al. Recombinant protein production by large-scale transient gene expression in mammalian cells: state of the art and future perspectives. Biotechnology Letters 29, 677-684 (2007). Link

Barnes, L.M., et al. Mammalian cell factories for efficient and stable protein expression. Current Opinion in Biotechnology 17 381–386 (2006) Link

Birch, J.R. et al. Antibody production. Advanced Drug Delivery Reviews 58 671 – 685 (2006) Link

Kunaparaju, R., et al., Epi-CHO, an Episomal  Expression System for Recombinant Protein Production in CHO Cells. Wiley Periodicals, (2005) Link

Wurm, F.M. Production of recombinant protein therapeutics in cultivated mammalian cells. Nature Biotechnology 22 No. 11 (2004) Link

 

In Vitro expression system

Johnston W & Alexandrov K (2014) Production of Eukaryotic Cell-Free Lysate from Leishmania tarentolae. Cell-Free Protein Synthesis, Methods in Molecular Biology, eds Alexandrov K & Johnston WA (Humana Press), Vol 1118, pp 1-15.

Kovtun O, Mureev S, Johnston W, & Alexandrov K (2010) Towards the construction of expressed proteomes using a Leishmania tarentolae based cell-free expression system. PLoS One 5(12):e14388.

Kovtun O, et al. (2011) Leishmania cell-free protein expression system. Methods 55(1):58-64.

Mureev S, Kovtun O, Nguyen UT, & Alexandrov K (2009) Species-independent translational leaders facilitate cell-free expression. Nat Biotechnol 27(8):747-752.