A recombinant protein has been produced in a laboratory using cells transfected with DNA engineered to carry the gene for a desired polypeptide. Recombinant proteins can have the same amino acid sequence as the corresponding naturally occurring (wild-type) protein, or have their sequence modified for improved properties such as solubility or production yield.

What are recombinant proteins used for?

There are myriad applications for recombinants proteins in biomedical research, as well as diagnostics and therapeutics. Recombinant proteins have become an important tool in various areas of science. Laboratory uses for recombinant proteins include:

Biologically active proteins

The above applications require that the recombinant protein be biologically active; that is, the protein is recognized by cells and cause changes in those cells. Bioactivity can be measured in an appropriate cell-based assay and quantified as a specific activity or EC50.

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Non-bioactive recombinant proteins may be used as standards in protein analysis studies including immunoassays such as western blotting, ELISA, gel shift, and immunohistochemistry.

Types of recombinant proteins

Many biologically important classes of recombinant proteins are available commercially, obviating the need to express, purify, and validate commonly used bioactive recombinant protein(s).

Major types of recombinant proteins include:

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Recombinant protein grades

When choosing a recombinant protein for a specific application, it helps to know which levels of quality control and documentation are required.

Research use only (RUO)

Research-grade recombinant proteins are suitable for a wide variety of life science research applications including development of cell models, maintaining cell phenotypes, and in vitro assays.

See specifications for Gibco PeproTech RUO proteins

Animal-origin free

Designed and manufactured to mitigate the risk of contamination from animal-borne pathogens such as viruses and BSE, animal-origin free recombinant proteins are produced without the use of any animal-derived reagents, purification media, etc.


As an additional safeguard against animal pathogen contamination, animal-free recombinant proteins are produced in a dedicated animal-free laboratory under strictly controlled manufacturing conditions.

Learn more about PeproTech animal-free recombinant proteins

GMP grade

GMP-manufactured recombinant proteins undergo extensive testing and are accompanied by documentation to support projects/applications that require this level of rigor.

Learn more about PeproGMP recombinant proteins

Frequently asked questions about recombinant proteins

Bioassays are intended to measure the biological activity of a given growth factor or cytokine. In most of the cases, the bioassays are cell-based tests using different indicator cells such as primary cells or cell lines. Commonly used bioassays include cell proliferation assay, chemotaxis assay, cytokine production assay, and cytotoxicity assay. The biological activity of a given cytokine is expressed as ED50, which represents the concentration of the cytokine that induces 50% of the maximum response.

The specific activity of a biologically active protein can be determined using the following equation:
1 x 106 / ED50 (ng/mL) = specific activity (units/mg)

The ED50 (a.k.a EC50) can be found on the CoA for the recombinant protein, but we advise determining the ED50 of a given recombinant protein in your functional assay system.

For additional information on ED50 and its relationship with specific activity,  please refer to our Tech Tip.

First, centrifuge the container to concentrate the powder at the bottom of the tube. In general, we recommend reconstitution to a concentration of 0.1 to 1.0 mg/mL. Most proteins can be reconstituted with the addition of sterile, distilled water. However, the product data sheet or CoA will indicate when a diluent other than water is required. Recommended solutions, carrier protein concentrations and extended storage conditions can also be found on these documents.

In general, we recommend that lyophilized recombinant proteins be stored at –20°C, but short-term storage at 4°C or room temperature is permissible. For reconstituted protein solutions, we recommend that you make working aliquots containing at least 10 μL of protein solution and store at –20°C to –80°C. Do not allow multiple freeze-thaw cycles. Product-specific instructions for storage of lyophilized and reconstituted recombinant proteins are provided on either the product manual, data sheet, or certificate of analysis (CoA).

Recombinant proteins are usually formulated without carrier proteins or additives (e.g., BSA, HSA, sucrose, etc.). As a result, during lyophilization the protein product may be deposited on the vial as a thin, and sometimes invisible, film instead of a pellet. The size of the pellet, if any, is not directly related to the quantity of the recombinant protein in the vial.

To ensure complete recovery of protein product, before opening a vial of lyophilized recombinant protein, we recommend centrifuging it for 20–30 seconds to drive any protein that may be lodged in the cap or on the side to the bottom of the vial. After reconstitution, you can confirm the presence of product protein by running a small amount on SDS-PAGE. In general, a protein band with expected size should be visible with as little as 10 ng of protein loaded on an acrylamide gel.

Learn more about recombinant proteins and their applications

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Recombinant Proteins Support Center

Find Getting Started guides, protocols, troubleshooting, and other resources

Recombinant proteins FAQs

Search the database to find answers to your questions

Contact general support

Get technical or customer support for any recombinant protein; find SDS, CoA, and phone numbers based on a specific product

Contact GMP support

Get in touch with GMP technical and regulatory experts

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Intended use of the products mentioned on this page vary. For specific intended use statements please refer to the product label.

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