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Cell-Free Protein Expression

Cell-Free Protein Expression

Cell-free protein expression can be performed in just a few hours using mRNA templates in translational systems, or DNA template (plasmid DNA or PCR fragments) in coupled transcription and translation systems, without the use of whole prokaryotic or eukaryotic cells. For DNA-based cell-free expression, Promega’s coupled transcription and translation (TNT®) systems offer researchers time-saving alternatives for eukaryotic in vitro transcription and translation by coupling these processes in a single tube format.

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26 Products

Accessory Reagents


Input Nucleic Acid

Kits and Reagents

Shop all Cell-Free Protein Expression

TnT® Starter Bundle

A combination of kits to get you started in cell-free expression and detection. Use for in vitro analysis of protein:protein or protein:nucleic acid interactions, or to verify the ability of your clone to express protein.

L1210, L1215

Canine Pancreatic Microsomal Membranes

Evaluate signal peptide cleavage, membrane insertion, translocation and core glycosylation. Compatible with TnT® Lysate, Rabbit Reticulocyte Lysate and Flexi® Lysate Systems.


T7 Sample System

Optimize gene expression with four in vitro translation test systems that use RNA generated by a T7 promoter.


pCMVTnT™ and pTnT™ Vectors

Convenient expression of cloned genes in vitro or in vivo. pCMVTnT™ Vector contains a CMV enhancer/promoter region, which enables strong constitutive expression in many cell types, while RNA phage promoters enable RNA synthesis in vitro.

L5620, L5610

TnT® T7 Quick for PCR DNA

Coupled transcription/translation system for optimum protein expression from PCR templates.


Rabbit Reticulocyte Lysate, Nuclease-Treated

Identify mRNA species, characterize proteins, investigate transcriptionl/translation control.


Luciferase SP6/T7 Control DNAs

Used as functional controls in TnT® Quick Coupled and TnT® Coupled Transcription/Translation Systems. The Control DNAs contain the gene for luciferase under transcriptional control of a phage RNA T7 or SP6 polymerase promoter and a 30-base pair poly[d(A)/d(T)] tail.

L4741, L4821

pGEM® β-Gal Control DNA

Contains coding sequence for β-galactosidase downstream of an E. coli wildtype lacZ promoter. Use as positive control in the E. coli S30 Extract System for Circular DNA.


TnT® Coupled Reticulocyte Lysate Systems

A single-tube, coupled transcription and translation system.

L4600, L4601, L4610, L4611, L4950, L5010, L5020

Potassium Chloride

2.5M solution to supplement TnT® reactions.


Magnesium Acetate

25mM magnesium acetate.


Luciferase Control RNA

A unique functional control for in vitro translation reactions. An uncapped in vitro-transcribed RNA containing a 30-base poly(A) tail that produces functional luciferase when translated. Control reactions are monitored by a luciferase assay.


Flexi® Rabbit Reticulocyte Lysate System

Translation reaction optimization for Mg2+ and K+ concentrations and the option to add DTT. The endogenous Mg2+ concentration of each lysate batch is stated in the product information to aid in optimizing reactions.


Amino Acid Mixtures

The complete mixture is an aqueous solution containing 1mM each of the 20 essential amino acids, compatible with Flexi® Lysate, TnT® Lysate and standard Rabbit Reticulocyte Lysate Systems, and the Wheat Germ Extract and E. coli S30 Systems. Amino Acid Mixtures are also available without cysteine, methionine and cysteine, leucine or methionine.

L4461, L4471, L5511, L9951, L9961

Wheat Germ Extract

Contains components needed for protein synthesis (tRNA, ribosomes, initiation, elongation and termination factors) yet is cleared of endogenous amino acids, mRNA and plant pigments to minimize background translation.


Showing 26 of 26 Products

What are Cell-Free Expression Systems?

Cell-free expression systems provide the tools for protein production without the cell itself. These tools include macromolecular components required for translation such as ribosomes, tRNAs, aminoacyl-tRNA synthetases, initiation, elongation, and termination factors. The cell-free expression approach is the fastest way to correlate phenotype (function of expressed protein) to genotype. Furthermore, cell-free protein expression systems are indispensable for the expression of toxic proteins, membrane proteins, viral proteins, and for proteins that undergo rapid proteolytic degradation by intracellular proteases. The most popular eukaryotic translation systems originate from either rabbit reticulocyte lysates (RRL) or wheat germ extracts (WGE).

The two main formats of cell-free expression systems are mRNA-based translation systems and DNA-based coupled transcription and translation systems from prokaryotic and eukaryotic sources. Cell-free mRNA translation systems are used for protein expression of either in vitro transcribed mRNA or mRNA isolated from tissues or cells. These systems are used to express single proteins as well as multiple proteins in high-throughput applications, such as display technologies. Cell-free translation systems are also useful for functional and structural RNA analysis, or to study aspects of the translational machinery. Cell-free DNA translation systems are used for a variety of applications in low- to high-throughput functional genome and proteome analyses.

We offer a complete portfolio of protein analysis products supported by a growing library of educational resources, including technology guides, on-demand webinars, scientific articles and protocols.

Use the links below to learn more about protein analysis products, or to explore learning resources covering topics such as in vitro protein expression, protein purification methods and live-cell protein interaction analysis.