Expression systems are genetic constructs designed to produce a protein. These consist of genes encoded by the DNA, facilitating medical research and furthering commercial production of therapeutics. To synthesize a particular protein, the DNA must be transcribed into RNA, which is then further translated into polypeptide chains that make up the primary structure of proteins. The process of synthesizing proteins from RNA along with bringing in modifications to it is commonly highlighted under the process of protein expression systems.
Understanding Protein Expression Systems
So, what are protein expression systems, and how are they relevant in today’s medical industry?
In the simplest of words, protein expressions refer to how proteins are synthesized, modified, and regulated in living organisms. Doing this is extremely crucial in investigating the function, structure, and utility of various proteins of interest.
The general strategy adopted for protein expression consists of transfecting cells with DNA templates and letting these cells translate the protein of interest. The process of the protein expression system depends entirely on the protein of interest, the quantity of protein of interest, and the application of protein of interest.
Protein Construction Using Recombinant Proteins
Not familiar with how proteins are constructed? It sounds easier than it is. Through a chemical synthesis process utilizing artificially generated protein templates, which are better known as “recombinant proteins”, living organisms are manipulated to build proteins based on the given genetic information, supplied in the form of DNA. The gene is isolated and cloned, after which the process of transfection of host cells with a DNA vector takes place. As a result, host cells produce proteins of interest.
Through the process, a variety of proteins of interest are produced. However, these are expressed in the form of other organisms. These include yeast, bacteria, insect, and animal cells. Due to the difference in the organism, some notable issues arise during the expression’s overview. Conversely, such problems are worked around using the right system for the specific application. For example, genes for recombinant proteins are often altered and tweaked to make the protein more stable. Similarly, regulating the rate at which the recombinant proteins are reproduced is another way of overcoming the challenges at hand.
The inclusion of recombinant protein expression technology has certainly revolutionized all aspects of life sciences. Many credible organizations have taken it upon themselves to develop advanced protein expressions, such as Trichoderma Reesei, a strain that can completely transform tens of industries across the globe, from the textile industry to the agricultural sector. Hence, it is essential to carefully choose the expression system to stay far from the confronts of the process.
Analyzing the Main Expression Systems
Diving deeper into the variety of expression systems, we will highlight the following four central systems for the expression of recombinant proteins:
Bacterial Expression Systems
Quite often, investigators keep bacterial expression systems as the first choice for the production of recombinant proteins. Also known as E. Coli protein expression systems, bacterial expressions are well-utilized, especially when it comes to larger samples. A fast growth of bacteria and rapid biomass accumulation, paired with low production cost, gives a robust analysis. Using bacterial expression systems assists in the wide high-quality application, ranging from antibody generation to protein interaction research.
However, much like all expression systems, some obstacles prevent complete reliance on bacterial expression systems. These obstacles include quality concerns with larger, more complex protein structures. In such cases, other expression systems are recommended.
Common Application:
- Structural and functional analysis.
- Antibody generation.
- Protein interaction.
Yeast Expression Systems
Scientifically highlighted as Saccharomyces Cerevisiae, yeast expression systems are another highly developed, advanced genetic system consisting of reduced time input, highly affordable production cost, and ease of use when producing recombinant proteins.
If you know a thing or two about these microorganisms, you might be familiar with the fact that yeasts can carry plasmids. This quality makes it extremely easy for the expression system to insert the gene sequence of interest, producing the desired protein without harmful encounters to protein production. Plus, it is extremely easy to scale up production when using yeast expression systems.
Such suitable characteristics certainly make it every investigator’s next best alternative to use during the production of recombinant proteins.
Common Applications
- Structural and functional analysis.
- Antibody generation.
- Protein interaction.
Mammalian Cell Expression Systems
Another popular method for expressing recombinant proteins is the mammalian cell expression system. While many researchers are not fully convinced with the delayed outcomes of this process, including reduced efficiency and low levels of proteins expressed, the method is still utilized in some circumstances.
To make the expression system stronger, cell lines like HEK293 and CHO have been developed for stable expression and transient upshots. HEK293 assists in transfecting, using liposomes and calcium. Similarly, CHO is used for expressing larger quantities of recombinant proteins. Nonetheless, it can be somewhat difficult scaling up the mammalian cell expression system, regardless if the cell line is used for aiding the overall process. The expansion process may or may not roughly take three months.
Common Application:
- Functional and structural analysis.
- Antibody production and virus production.
- Expression of complex proteins.
Insect Cell Expression Systems
When all else fails, cell lines derived from insect cells, including Spodoptera Frugiperda, Sf9, and Sf21 are commonly used as recombinant protein expression systems. These can be highly expressed during the last phases of the lytic cycle before cell lysis, making them suitable to generate cytoplasmic proteins and secreted proteins. The production of more than one protein of interest makes this expression system foolproof when compared head-on with the rest.
Common Application:
- Expression of protein complexes.
- Expression of intracellular proteins.
- Virus production.
Now that you are familiar with what protein expression systems are, what their common application is, and how they compare with each other, it will be much easier for you to overview the various alternatives you have at hand when choosing the right expression system for your study. Having an in-depth understanding of the main expression systems can give you a definitive edge in streamlining your research as a core investigator.
