When you want to characterize a gene or protein of interest, you must first study its function. In this molecular age, obtaining a cDNA of your gene of interest is not difficult.

To express the cDNA as a protein, IE. a recombinant protein, one can then easily perform functional studies using purified recombinant protein.

Once you have a purified protein can lead to:

* Experience interaction Protein-protein
* Kinetics of enzymes
* Functional Studies of the protein
* Structural Studies – including protein crystallization, the protein structure and NMR.
* You can also use protein to make antibodies for further experiments.

There are two main systems for the expression of the recombinant protein. Once you get your cDNA copied, you must decide where you want to boost your protein. This will (usually a prokaryotic (bacterial) or eukaryotic yeast or mammalian cells). Choosing your system decide what vehicle you need to copy your cDNA as there are various promoters that function in Escherichia coli and others that work well with yeast or mammalian systems.