Recombinant Fusion Protein and its uses

What is Recombinant Fusion Protein?

Definition: Recombinant Fusion Protein are proteins made by rDNA technology that involves joining of two or more genes from different sources, transcribed and translated as a single polypeptide. 

Let’s explain with an example; In the figure, there is a fusion protein GFP human alpha tubulin fusion protein. Green Florescent Protein (GFP) joining, enables its subcellular localization under Florescence microscope. GFP emits green light when excited by blue or UV light. In the figure, the green colour is the region where tubulin is present inside cells and we know that tubulin forms the cytoskeleton.

Fusion partners and its properties

The common fusion partners or tagging proteins are β-galactosidase, luciferase and GFP.

• β-galactosidase has the advantage of numerous commercially available substrates, including some that produce a colored product and some that lead to the production of light.
• Luciferase and GFP both produce light, and can be visualized directly or quantified using a fluorometer. Luciferase requires its substrate, luciferin, as well as ATP, O₂, and Mg²⁺.
• GFP does not require a substrate. It emits green light when excited by blue or UV light, and in many cases can be used on live, intact cells and organisms.

How e make Fusion protein?

We have to make a gene construct with a promoter, gene of protein of interest and fusion protein (see figure). Then insert this construct into a suitable vector and transform into a suitable host like E.coli. On transcription and translation, we get a fusion protein.

Uses of Recombinant Fusion Protein

• Purification of cloned genes

       In recombinant insulin production, Fusion protein of Insulin A chain and B chain is formed with fusion partner β-galactosidase. β-galactosidase enables easy purification by affinity chromatography.

(Video on recombinant insulin production for your reference)

• As reporters of expression level
• Histochemical tags to visualize of location of proteins in cell, tissues Eg: GFP we have already discussed.
• As gene expression inducer

In recombinant insulin production, Fusion protein of Insulin A chain and B chain is formed with fusion partner β-galactosidase. Lactose, the substrate of β-galactosidase in the medium induces gene expression, thus ensuring efficient transcription of our protein of interest also.

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