Protein Expression Techniques

Protein Expression Techniques

If you have a gene of interest, you first want to find out what is its function. What does this protein do in the cell? It is easy these days to obtain the cDNA of your gene of interest. If you can express this cDNA as a protein (recombinant protein), you can easily do functional studies using the purified protein such as:

- enzymology studies

- protein-protein interaction studies

- protein functional studies

- Structure NMR, protein crystalization and protein structure (obtain the 3-D crystal structure of the protein)

- use the protein as an immunogen for antibody production

Systems for Protein Expression

Prokaryotic Systems E.Coli

Advantages of prokaryotic recombinant protein expression systems :

  • ease of culture
  • rapid cell growth
  • expression is inducible using IPTG
  • purification is pretty simple
  • many commercial kits available

Disadvantages of recombinant prokaryotic protein expression systems :

  • most proteins become insoluble and are very difficult to recover as functional proteins
  • post-translational modifications are not added by bacteria
  • thus your protein may not be functional

Eukaryotic Systems

Yeast, mammalian cells, and baculovirus expression systems are great eukaryotic systems for expressing recombinant proteins.
Advantages of eukaryotic protein expression systems :

  • you can easily achieve very high levels of expression
  • easy to purify using tags (His, Myc)
  • can obtain plasmids that secrete your protein (you can thus keep growing the yeast and collecting from media)
  • proteins have post-translational modifications!

Disadvantages of recombinant eukaryotic protein expression systems :

  • cells grow slower