The modern view of cells has made it clear that genes encode for proteins. In both, prokaryotic and eukaryotic cells, controlled and integrated actions of genes can produce specific sets of proteins with characteristic structures that carry specific modifications needed for the cells to function. This process is called “gene expression”, which refers to the conversion of the information encoded in a gene first into messenger RNA and finally to a protein. Protein expression also refers to processes which describe how living cells or organisms synthesize, modify and regulate proteins. In protein research, protein expression can now also refer to the use of laboratory techniques required for the manufacture of proteins. Furthermore, protein expression has become an important laboratory technology in biochemistry, molecular biology and protein research as well as other scientific research fields which require functional proteins for their research. Expressed protein products that are functional and show characteristics similar to their native counterparts are very useful for further research such as the determination of the three dimensional structure of proteins, as chemical tools or probes, or as new types of drugs, among others. In addition protein expression can provide substrates or enzymes required for further analysis. The study of proteins is far more complex than the study of genes. This is due to the fact that structures and functions of proteins are more complex and diverse. The ability to express functional proteins enables researchers to study them in vitro more easily.
Recombinant protein expression refers to the manufacture of proteins derived from recombinant DNA. This technique is now routinely used in molecular biology and in pharmaceutical production of protein and peptide based hormones. Many proteins that were historically derived from animal sources can now be synthesized by recombinant protein expression followed by harvesting and purifying them from host cells. However, before the start of a large scale protein expression, a small pilot scale protein expression is usually performed. Many chemically competent E. coli cells, suitable for transformation and protein expression, are now available as research kits. Other commonly used protein expression systems include cell systems derived from yeast, baculovirus/insect and mammalian cells, and more recently filamentous fungi such as commercially relevant fungus Myceliophthora thermophila. Also of note, CHO cells now appear to be the expression system of choice for the production of functional antibodies or other larger biosimilar proteins.
There are many books available for hands-on instructions on cloning and expressing proteins. Many of these books tend to simplify the science of recombinant protein expression. The required steps of DNA encoding a target protein and cloning downstream of a promoter into an expression vector followed by the introduction of the modified vector into a host cell, and the production of the desired protein by the cell’s protein synthesis machinery tend to be simplified. However, in practice, the many factors influencing this process can make the expression of a protein quite challenging. Factors such as proper protein folding, correct post-translational modification, or the insertion of the expressed protein into a biological membrane, are influenced by the selection of the expression system and may complicate the protein expression process. Furthermore, the activity of some proteins may even be detrimental to the host cells. As such, no single foolproof solution exists for the successful production of all recombinant proteins. Access to a wide range of expression tools and a willingness to explore multiple approaches are key to sucessful protein expression.
Biosynthesis Inc. has extensive expertise in the synthesis and production of biological reagents such as antibodies, oligonucleotides, peptides, proteins, recombinant proteins, and protein conjugates, as well as other research chemicals which will help you with your protein expression needs.