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Mammalian Protein Expression

VectorBuilder provides extensive expertise in producing recombinant proteins in mammalian cells. The mammalian recombinant protein expression system enables the target proteins to be expressed in their most natural state, making it the preferred approach for generating therapeutic proteins, vaccines, and antibodies. We offer recombinant protein production in HEK293 cells using a highly optimized transient transfection platform and in CHO cells upon request.


  • Eukaryotic proteins in their most native state with proper folding
  • Contains all necessary post-translational modifications
  • Both transient protein expression and stable cell line generation services are available

Service Details


Price and turnaround Price Match
Service Module Brief Description Deliverables Price (USD) Turnaround
Vector design and cloning Our vector design includes fusion partner selection, purification tag selection, and codon optimization. This is followed by gene synthesis and cloning into the mammalian protein expression vector. E. coli glycerol stock From $160 1-2 weeks
Pilot-scale expression and purification Mammalian cells, such as HEK293 cells, will be transfected. If feasible, 0.1-0.5 mg of purified target proteins * can be produced, and quality control (QC) will be performed.
  • 0.1-0.5 mg purified proteins (if feasible)
  • COA
From $1,800 3-4 weeks
Production-scale expression and purification Scaled up production of >100 mg of purified proteins.
  • Up to 100+ mg purified proteins
  • COA
Please inquire

* Purification methods will be determined based on the construct design and protein characteristics. 

Shipping and storage

The default deliverable for vector cloning is E. coli glycerol stock. Upon request, small amounts of plasmid DNA can be provided if available without additional charge. Most of our recombinant proteins are delivered as frozen liquid on dry ice. Upon receipt, they should be stored at -20°C to -80°C under sterile conditions. Recombinant proteins typically remain stable for up to a year if stored properly. Additionally, we recommend aliquoting the recombinant proteins upon receiving and avoiding freeze-thaw cycles.

Quality control (QC)

All vectors cloned by VectorBuilder come with a 100% sequence guarantee. All recombinant proteins produced by VectorBuilder undergo stringent quality control. Default QC for most systems includes 1) validation of the protein expression vector by restriction digestion analysis and Sanger sequencing; and 2) determination of protein concentration and purity by A260/280 measurement and SDS-PAGE. Common additional QC services are shown in the table below, which can be provided upon request.

Additional QC services Method
Endotoxin test LAL
Protein characterization Western Blot
Intact MS (reduced)
Protein N-terminal sequencing
Host cell protein test
Tag removal Protease digestion
Kinetics and affinity analysis Octet
Pathogen testing panel for rodents

Technical Information

Vector system

Please visit our vector guides on mammalian expression vector systems.

Case study
Mammalian protein expression QC

Figure 1. Characterization of a recombinant protein produced in HEK293 cells. (A) SDS-PAGE analysis shows the molecular mass of the recombinant protein, and the purity was determined to be ≥ 95%. (B) The purity was determined to be ≥ 90% by SEC-HPLC. (C) The biological activity of the recombinant protein was measured in an antibody binding assay. The EC50 is between 0.6 and 2.0 ng/ml.

How to Order

Customer-supplied vectors

If customer-supplied materials are needed, please send them to us following the Materials Submission Guidelines. Please strictly follow our guidelines to set up shipment to avoid any delay or damage of the materials. All customer-supplied materials undergo mandatory QC by VectorBuilder, which may incur $100 surcharge for each item. Please note that production may not be initiated until customer-supplied materials pass QC.


Which recombinant protein expression system should I choose?

All recombinant protein expression systems have their pros and cons which should be taken into consideration while selecting the optimal system for your project. The table below summarizes the pros and cons of each system.

Recombinant protein expression system Pros Cons
  • Cost-effective
  • Short production time
  • Technically simple
  • Can be scaled up easily
  • High protein yield
  • Proteins lack post-translational modifications
  • Codon usage is different from that of eukaryotes
  • Difficult to express certain proteins due to the accumulation of inclusion bodies
  • Some proteins are toxic and can inhibit bacterial growth
Mammalian cells
  • Produces proteins in their most natural state with all necessary post-translational modifications and proper folding
  • Suitable for secretory and membrane proteins
  • Most appropriate for producing therapeutic proteins
  • Long production time
  • Requires complex growth conditions
  • Scaling up can be difficult
  • Not suitable for intracellular proteins due to low yield
  • Performs majority of complex post-translational modifications and protein folding
  • Suitable for secretory, intracellular, and membrane proteins
  • Can be used for producing large protein complexes
  • High levels of protein expression compared to other eukaryotic expression systems
  • Highly scalable due to high-density, suspension cell cultures
  • Long production time
  • Requires complex growth conditions
  • Technically challenging
Cell-free system
  • Time-efficient synthesis completed in 3 hours
  • No need for live cells in the production of toxic, complex, or unstable proteins
  • Suitable for high-throughput protein expression and screening
  • Easy procedure compatible with automated processes
  • Easy to optimize the conditions
  • Limited modifications are available
Which protein tag should I use?

Tags are frequently utilized for recombinant protein production. They streamline the purification process, and certain tags have demonstrated improvement in protein solubility, yield, or purity. If the tag is attached to the protease cleavage site, it can be removed after purification, and the efficiency of cleavage varies depending on the target protein. The careful selection of an appropriate tag is crucial for downstream protein expression and purification. The table below provides an overview of commonly used tags along with their advantages and limitations.

Tag Commonly applied system Advantages Limitations
GST Bacteria, insect
  • Largely preserve the native structure of the protein
  • Enables protein purification under mild conditions
  • Easy cleavage
  • Enhances the solubility and expression of the protein
  • Large tag size
  • Dimerization may impact the target protein
  • Not suitable for purifying proteins under denaturing conditions
His All
  • Small tag size, therefore less impact on the protein
  • Low cost for metal-affinity chromatography
  • Low immunogenicity
  • Suitable for purifying proteins under denaturing conditions
  • Other endogenous metal-binding proteins in microbial hosts may be co-purified, therefore optimization is usually required
  • Does not facilitate protein folding and solubility
SUMO Bacteria, insect
  • Facilitates protein folding
  • Enhances the solubility and expression of the protein
  • May undergo non-specifically cleavage by other bacterial proteins
  • Not suitable for purifying proteins under denaturing condition
Flag Mammalian cells, insect
  • Small tag size, therefore less impact on the protein
  • Easy detection
  • Low non-specific binding
  • Poor efficacy for purification
MBP Bacteria, insect
  • Enhances the solubility and expression of the protein
  • Large tag size
  • Not suitable for purifying proteins under denaturing conditions
Fc Mammalian cells, insect
  • Enhances the solubility and expression of proteins
  • Suitable for secreted protein
  • Large tag size

For more information regarding tags, please visit protein tags.

Should I use HEK293 or CHO cells for the expression of my protein?

For transient transfection, we recommend HEK293 (Human Embryonic Kidney 293) as the first choice. HEK293 cells are easy to transfect, with well-established and efficient procedures that save you time and money. Furthermore, HEK293 cells are easily passaged and maintained in R&D labs and exhibit high levels of protein expression.

In contrast, CHO (Chinese Hamster Ovary) cells pose some transfection challenges. However, they are more suitable for the biopharmaceutical industry, particularly in the production of therapeutic antibodies or proteins. More than 70% of biotherapeutics are manufactured using this cell line.